Composite article with co-planar electrodes

ABSTRACT

A composite article has 1) a dry piezoelectric layer, and 2) a pair of non-electrically-connected co-planar patterned electrodes that are arranged contiguously with an opposing surface of the dry piezoelectric layer. Each electrode essentially has (a) an electrically-conductive material; and (b) particles having a Young&#39;s modulus that is different from the Young&#39;s modulus of the (a) electrically-conductive material by at least 10%.

RELATED APPLICATIONS

Reference is made to the following commonly assigned and co-filed patentapplications:

-   U.S. Ser. No. 15/841,459, filed on Dec. 14, 2017, by Benedict and    Sieber, and entitled “Electrically-conductive Compositions”;-   U.S. Ser. No. 15/841,483, filed on Dec. 14, 2017, by Benedict and    Sieber, and entitled “Silver-containing Electrically-conductive    Compositions”;-   U.S. Ser. No. 15/841,519, filed on Dec. 14, 2017, by Benedict and    Sieber, and entitled “Piezoelectric Composite Articles”;-   U.S. Ser. No. 15/841,583, filed on Dec. 14, 2017, by Benedict and    Sieber, and entitled “Composite Article with Dielectric Layer”;-   U.S. Ser. No. 15/841,610, filed on Dec. 14, 2017, by Benedict,    Sieber, and Tucker, and entitled “Piezoelectric Article with    Dielectric Layer and Co-Planar Electrodes”;-   U.S. Ser. No. 15/841,655, filed on Dec. 14, 2017, by Sieber and    Benedict, and entitled “Piezoelectric Capacitor”;-   U.S. Ser. No. 15/841,677, filed on Dec. 14, 2017, by Sieber and    Benedict, and entitled “Piezoelectric Capacitor with Co-Planar    Patterned Electrodes”;-   U.S. Ser. No. 15/841,706, filed on Dec. 14, 2017, by Sieber and    Benedict, and entitled “Kinetic Piezoelectric Capacitor with    Co-Planar Patterned Electrodes”;-   U.S. Ser. No. 15/841,731, filed on Dec. 14, 2017, by Sieber and    Benedict, and entitled “Inertial Piezoelectric Capacitor with    Co-Planar Patterned Electrodes”;-   U.S. Ser. No. 15/841,761, filed on Dec. 14, 2017, by Sieber and    Benedict, and entitled “Kinetic Piezoelectric Device”;-   U.S. Ser. No. 15/841,796, filed on Dec. 14, 2017, by Sieber and    Benedict, and entitled “Inertial Piezoelectric Device”; and-   U.S. Ser. No. 15/841,827, filed on Dec. 14, 2017, by Benedict and    Sieber, and entitled “Method for Providing Piezoelectric Devices.”

FIELD OF THE INVENTION

This invention relates to a composite article that can be used toprovide improved piezoelectric effects. This composite article has apiezoelectric layer and a pair of non-electrically-connected co-planarpatterned electrodes arranged contiguously with an opposing surface ofthe piezoelectric layer. One or more of the electrodes contains unique(b) particles to provide the improve piezoelectric effect.

BACKGROUND OF THE INVENTION

Piezoelectric materials are materials that can generate charge andprovide voltage when placed under mechanical stress (“piezoelectriceffect”), and conversely can be deformed under an applied electricalfield (the “converse piezoelectric effect”). In general, piezoelectricmaterials exhibit these two reciprocal effects characterized by thepiezoelectric constants “d” and “g”, respectively. Commonly madepiezoelectric constant measurements include the “D₃₃” piezoelectriccharge coefficient (or “d₃₃”, in units of picocoulombs per Newton, pC/N)and the “G₃₃” piezoelectric voltage coefficient (or “g₃₃”, in units ofpm/V). These piezoelectric coefficients express the piezoelectricresponse of a material when stress or voltage is applied parallel to thecrystallographic c-axis of the piezoelectric material or parallel to thepoling direction of the piezoelectric layer and the material response isalso measured along to the crystallographic c-axis of the piezoelectricmaterial or along the poling direction of the piezoelectric layer.

Piezoelectric devices have many applications such as for high voltagegeneration (for example, as gas lighters producing a spark),microactuators, microbalances, acoustic generators (including ultrasoundgenerators), vibration sensors, and other devices known in the art.

A common piezoelectric material is lead zirconate titanate (PZT) but asone might suspect, such material raises both environmental and publichealth concerns relating to both production and use because of thepresence of lead. U.S. Pat. No. 6,469,421 (Wakabayashi et al.) describesthe use of a layer of ultra-fine particles of the same material in a PZTpiezoelectric layer. While lead zirconate titanate performs well, it hasproven difficult in recent years to find materials with comparableperformance so that PZT can be replaced. It is also difficult to makeeither thick or thin film piezoelectric devices of high sensitivity, andthus, efforts are being undertaken to find improved materials withoutthe presence of lead.

A study of reciprocity effects using a layer of loose tin particles onthe surface of a piezoelectric device (transducer) comprised of poly(vinylidene fluoride) (PVDF) that is a piezoelectric material isreported by Faust and Lakes in Physica Scripta 90 085807 (2015). Whilethe work of these investigators suggests that non-uniform stress fieldsmay change the piezoelectric charge constant d₃₃, their approach was touse a loose powder on the surface of the piezoelectric material. Thisloose powder can be readily dislodged from the piezoelectric layer andany change in d₃₃ is thereby diminished or lost entirely. Thus, thetransducer they proposed is mechanically unstable and impractical forany industrial use.

Flexoelectric piezoelectric composites are described in U.S. Pat. No.7,791,248 (Cross et al.) as having unique shapes in order to modify theelectrical signals obtained from applied forces. The materials describedin this patent are rigid bodies and the teaching does not lead itself tousing flexible materials. In addition, flexoelectric effects aregenerally smaller than piezoelectric effects, as noted by Krichen andSharma in the J. Appl. Mech. 83, 030801-1 to 030801-5 (2016).

It is recognized by those skilled in the art of piezoelectric materialsthat piezoelectric polymers (such as PVDF), in general, have lowerpiezoelectric coefficients than crystalline inorganic piezoelectricmaterials such as PZT and that the lower piezoelectric coefficients ofpiezoelectric polymers have hampered the development of uses for thesematerials. Many uses of piezoelectric materials will benefit from anymethod for improving the piezoelectric constants (for example, the d₃₃piezoelectric charge coefficients) of the material. Thus, there is aneed for improved piezoelectric materials, methods of improving thepiezoelectric coefficient of piezoelectric materials, improved methodsof packaging piezoelectric materials to enhance the piezoelectriccoefficients of the piezoelectric materials, and improved devicescontaining piezoelectric materials with enhanced piezoelectriccoefficients.

Particularly, it is desirable to increase the magnitude of thefundamental piezoelectric coefficients d₃₃, d₃₁, or any otherpiezoelectric coefficients in order to improve the overall performanceof devices that utilize this piezoelectric coefficient for operation.

SUMMARY OF THE INVENTION

The present invention provides a composite article comprising:

1) a first dry piezoelectric layer (first dry PL) comprising apiezoelectric material and having first and second opposing surfaces,and

2) a pair of non-electrically-connected co-planar patterned electrodesthat are arranged contiguously with at least one of the first and secondopposing surfaces of the first dry PL, each of the pair ofnon-electrically-connected co-planar patterned electrodes consistingessentially of:

(a) an electrically-conductive material; and

(b) particles distributed within the (a) electrically-conductivematerial, the (b) particles having a Young's modulus that is differentfrom the Young's modulus of the (a) electrically-conductive material byat least 10%, and which (b) particles have a d50 of at least 500 nm andup to and including 500 μm and a polydispersity coefficient of less thanor equal to 3, provided that the weight ratio of the (b) particles tothe (a) electrically-conductive material is at least 0.01:1 and up toand including 10:1, provided that the weight ratio of the (b) particlesto the (a) electrically-conductive material is at least 0.01:1 and up toand including 10:1;

provided that:

when each of the pair of non-electrically-connected co-planar patternedelectrodes is arranged adjacent to an insulating substrate, it exhibitsa resistivity of less than 10,000 ohms-cm, and

optionally, each of the pair of non-electrically-connected co-planarpatterned electrodes further includes (c) a binder material that isnon-electrically-conductive and has a weight average molecular weight ofat least 5,000.

The electrically-conductive (EC-P) compositions prepared according tothe present invention enable inventive methods to prepare inventivecomposite articles (or composite electrodes) and devices having animproved piezoelectric charge coefficient d₃₃. Particularly, theinventive compositions, composite articles, and methods of use provide asimple means for improving the d₃₃ piezoelectric charge coefficient ofboth piezoelectric polymers and piezoelectric ceramics for use invarious devices. Thus, the present invention can provide piezoelectricdevices such as energy harvesters, capacitors, and sensors comprised ofpiezoelectric materials and electrodes that exhibit improved responses.

Approaches in the prior art to improve the performance of piezoelectricdevices concentrate on collecting charge from the direction of thelargest piezoelectric coefficient that is accessible given the geometryof a device (meaning the actual architecture of the device and how it ispoled). This is exemplified in the use of interdigitated electrodearchitectures in many known piezoelectric devices. These specializedelectrode architectures as currently practiced in the art do not affectthe fundamental piezoelectric coefficients of the piezoelectricmaterials used in device construction. An advantage of the presentinvention, particularly the composite article structure, is the abilityto directly manipulate and improve the piezoelectric charge coefficientd₃₃ of a device without depending upon its structure. This isfundamentally different from articles of the prior art that have beenreduced to practice by direct measurement of the fundamentalpiezoelectric charge coefficient d₃₃ for different composite electrodestructures.

Specifically, it has been discovered that an inventive composite article(or electrode) design including a dry piezoelectric layer (PL) and oneor more layers or co-planar electrodes containing (b) particles(described below), and devices prepared from such composite articles canenhance the piezoelectric response of piezoelectric materials measuredin terms of d₃₃. In some embodiments, the inventive composite articledesign comprises one or more dry electrically-conductive layers (dryECL-P's) containing a novel electrically-conductive EC-P compositioncomprising required (b) particles of certain characteristics and havinga different Young's modulus different from the one or more (a)electrically-conductive materials that are used in the dry ECL-P(electrode) to collect the charge generated by the dry piezoelectriclayer (dry PL).

In other embodiments, a dry PL is used with at least one dry dielectriclayer (dry DL-P) containing (b) particles as described below.

In many embodiments, the EC-P compositions are used to provide uniformlayers, but in some embodiments, non-electrically-connected co-planarpatterned electrodes can be prepared from an EC-P composition and suchelectrodes are not uniform layers and are not electrically connected toeach other. Yet, these non-electrically-connected co-planar patternedelectrodes also contain the (b) particles as defined below.

Details of the noted (b) particles are provided below. In someembodiments, the (b) particles are non-compressible but in otherembodiments, they are elastic and compressible. Moreover, the (b)particles can be either insulating or electrically-conductive. Inembodiments using silver nanoparticles as the electrically-conductivematerial, the d50 of the (b) particles is greater than the d50 of thosesilver nanoparticles.

Without being limited to a particular mechanism or theory, it isbelieved that the function of the (b) particles is to affect thedistribution of stress within the dry piezoelectric layer (dry PL) uponapplication of force to a dry ECL-P or dry DL-P surface or to thesurface of non-electrically-connected co-planar patterned electrodescontaining (b) particles, thereby affecting the magnitude of thepiezoelectric effect as measured as d₃₃. It is believed that when thedry ECL-P, dry DL-P, or non-electrically-connected co-planar patternedelectrode network is flexible and deformable during application ofstress (force), the stress distribution propagated throughout thatnetwork to the dry PL is primarily determined by the nature of the (b)particles and their distribution within the dry ECL-P, dry DL-P, ornon-electrically-connected co-planar patterned electrodes.

While it is possible for the outermost composite article surface to be“rough” and textured, it is not necessary for this to be the case fromthe presence of the (b) particles themselves. Rather, the change in thepiezoelectric charge coefficient d₃₃ of the dry PL is brought aboutmainly by the stress localization caused by the non-uniform mechanicalproperties of the dry ECL-P, dry DL-P, or non-electrically-connectedco-planar patterned electrodes (one or more pairs) within the compositearticle.

Those skilled in the art of piezoelectric materials recognize that themodels used to describe the piezoelectric response of a piezoelectricmaterial are based on the thermodynamic conditions where the applicationof physical force to the PL results in the creation of uniform stress inthe dry PL. The presence of (b) particles in a layer adjacent the dry PLprovides the potential of non-uniform stress fields in the dry PL duringforce application and this condition is outside of the scope of theconventional thermodynamic models. Since the conditions where the dry PLis under non-uniform stress fall outside of those described by acceptedthermodynamic based models that are familiar to those skilled in the artof piezoelectric materials, the response of a given dry PL with a givendry ECL-P, dry DL-P, or non-electrically-connected co-planar patternedelectrodes that are used to produce non-uniform stress in the dry PL is,therefore, unpredictable by accepted theory and cannot be suggested inany known art.

The unique embodiments of the present invention were ably demonstratedby disposing either an electrically-conductive EC-P composition ordielectric layer composition (D-P composition) containing (b) particlesover one or both supporting surfaces of a dry PL comprised of a suitablepiezoelectric material. It is believed that other methods can be used tocreate the inventive composite articles but the use of anelectrically-conductive EC-P or D-P composition described herein can beespecially useful for simple manufacturing methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional representation, not to scale, of aprior art composite article comprising a dry PL and a dry ECL.

FIGS. 2-16 are schematic cross-sectional representations, not to scale,of various embodiments of composite articles according to the presentinvention, each composite article comprising a dry PL and at least onedry ECL-P.

FIGS. 17-19 are schematic cross-sectional representations, not to scale,of various embodiments of composite articles according to this presentinvention, each composite article comprising a dry PL and at least onedry DL-P.

FIG. 20 is a graphical representation of particle size dispersity forthe silver nanoparticles used in Comparative Example 1 below.

FIG. 21 is a graphical representation of particle size dispersity forthe (b) particles used in Invention Examples 1-3 below.

FIG. 22 is a graphical representation of particle size dispersity forthe (b) particles used in Invention Examples 7-12 below.

FIG. 23 is a graphical representation of particle size dispersity forthe (b) particles used in Invention Examples 4-6 below.

FIG. 24 is a graphical representation of particle size dispersity forthe (b) particles used in Invention Examples 13-16 below.

FIG. 25 is a graphical representation of particle size dispersity forthe silver nanoparticles used in Comparative Examples 2-4 below.

FIG. 26 is a graphical representation of d₃₃ piezoelectric chargecoefficients as a function of preloaded force (Newtons) for ComparativeExample 5.

FIG. 27 is a graphical representation of d₃₃ piezoelectric chargecoefficients as a function of preloaded force (Newtons) for InventionExample 26.

FIGS. 28 and 29 are graphical representations of d₃₃ piezoelectriccharge coefficients as a function of delta force (Newtons) and preloadedforce (Newtons), respectively, for Invention Examples 45 and 46 below.

FIGS. 30a, 30b, and 30c are schematic diagrams of electromechanicalmodels for devices containing a composite article according to thepresent invention.

FIGS. 31a, 31b, and 31c are schematic diagrams of kinetic and inertialpiezoelectric devices.

FIGS. 32a-32c are schematic cross-sectional representations of severalembodiments of piezoelectric capacitors according to the presentinvention.

FIG. 33 is a schematic electrical diagram of a means of current andvoltage rectification.

FIG. 34 is a schematic representation of a kinetic piezoelectric deviceaccording to the present invention.

FIG. 35 is a schematic representation of an inertial piezoelectricdevice according to the present invention.

FIG. 36 is a schematic representation of an inertial energy harvesteraccording to the present invention.

FIG. 37 is a schematic representation of a “force-sensitive” capacitivetouch display according to the present invention.

FIG. 38 is a schematic representation of a “force-sensitive” resistivetouch display according to the present invention.

FIGS. 39 and 40 are exploded schematic perspective cross-sectional viewsof composite articles according to the present invention havingco-planar patterned electrodes with a dielectric material containing (b)particles.

FIGS. 41 and 42 are exploded schematic perspective cross-sectional viewsof composite articles according to the present invention havingco-planar patterned electrodes comprising (b) particles as describedbelow.

FIG. 43 is a schematic illustration of the use of a composite articledescribed below in Invention Example 49 comprising a dry DL-P arrangedover a dry ECL, where electrical contact is made to a first dry ECL by aplatinum wire in electrical contact with the dry ECL and to a second dryECL on an opposing surface of a dry PL.

FIG. 44 is a schematic illustration of the use of a composite articledescribed below in Invention Example 50 comprising a dry DL-P arrangedover a first dry ECL, where a complete circuit is made by contacting thedry DL-P on one surface and on a surface of a second dry ECL.

FIG. 45 is a schematic illustration of a composite article havingconcentric non-electrically-connected co-planar patterned electrodes.

FIG. 46 is a schematic illustration of a composite article havingserpentine non-electrically-connected co-planar patterned electrodes.

FIGS. 47A and 47B are schematic illustrations of articles describedbelow having patterned dielectric layers that are contiguous with a PLand ECL.

FIGS. 48A, 48B, and 48C are cross-sectional views of unimorph cantileverbeams (devices) described below in Examples 51 and 52.

FIGS. 49, 50, and 51 are graphical representations of data obtained byevaluating the reference and novel unimorph cantilever beams (devices)according to Examples 51 and 52.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is directed to various embodiments of thepresent invention and while some embodiments can be desirable forspecific uses, the disclosed embodiments should not be interpreted orotherwise considered to limit the scope of the present invention, asclaimed below. In addition, one skilled in the art will understand thatthe following disclosure has broader application than is explicitlydescribed for the discussion of any embodiment.

Definitions

As used herein to define various components of each EC-P composition,D-P composition, dry piezoelectric layer (PL), dryelectrically-conductive layer (ECL or ECL-P), dry dielectric layer(DL-P), discontinuous coplanar patterned electrodes, and other materialsused in the practice of this invention, unless otherwise indicated, thesingular forms “a,” “an,” and “the” are intended to include one or moreof the components (that is, including plurality referents).

Unless otherwise indicated, the piezoelectric layers,electrically-conductive layers (with or without (b) particles),dielectric layers (with or without (b) particles),non-electrically-connected co-planar patterned electrodes (with orwithout (b) particles), are meant to reference the “dry” form of suchlayers or electrodes, meaning that any solvents in their formation havebeen substantially (at least 95% of original solvent weight) removed. Itis understood that for some features of such layers or electrodes, the“wet” form can be the same as the “dry” form, but in practice, it is thedry form of such layers or electrodes that demonstrate the advantages ofthe present invention. Thus, identifiers of such layers, such as PL,ECL-P, and others, are meant to be the same as PL, ECL-P, and others,respectively.

Each term that is not explicitly defined in the present application isto be understood to have a meaning that is commonly accepted by thoseskilled in the art. If the construction of a term would render itmeaningless or essentially meaningless in its context, the term shouldbe interpreted to have a standard dictionary meaning.

The use of numerical values in the various ranges specified herein,unless expressly indicated otherwise, are considered approximations asthough the minimum and maximum values within the stated ranges were bothpreceded by the word “about.” In this manner, slight variations aboveand below the stated ranges may be useful to achieve substantially thesame results as the values within the ranges. In addition, thedisclosure of these ranges is intended as a continuous range includingevery value between the minimum and maximum values as well as the endpoints of the ranges.

As used herein to define the (b) particles, “non-compressible” meanseach (b) particle has a Young's modulus equal to or greater than theYoung's modulus of the electrically conductive layer without particles(ECL).

As used herein, “dry ECL” refers to a dry electrically-conductive layerthat does not contain (b) particles as are defined herein below. Suchdry ECL's are prepared from electrically-conductive compositions thatare outside the scope of the present invention but which comprise atleast an (a) electrically-conductive material and optionally a (d)binder material as described below.

As used herein, “dry ECL-P” refers to a dry electrically-conductivelayer prepared according to the present invention comprising theessential (b) particles described below. Such dry ECL-P must alsocomprise an (a) electrically-conductive material, and optionally a (d)binder material as described below.

As used herein, “dry DL-P” refers to a dry dielectric layer preparedfrom a dielectric (D-P) composition according to the present inventioncomprising the essential (b) particles described below, and at least onedielectric material.

As used herein, the term “non-electrically-connected co-planar patternedelectrodes” refers to two or more (a pair) dry electrically-conductiveelectrodes that are arranged in the same plane in a patternwise fashion,and which comprise at least an (a) electrically-conductive material, andoptionally (b) particles or (d) binder material, as described below.Such “dry electrodes” are thus arranged in a predetermined pattern asopposed to a uniform layer as is the case for the dry ECL and dry ECL-Pdescribed herein. Certain embodiments of such non-electrically-connectedco-planar patterned electrodes are described below in reference to FIGS.39-42.

As used herein to describe the relationship of various layers the term“contiguously with” means that such layers are arranged in arelationship so that they are adjacent. The term does not mean that theyare necessarily directly adjacent or in physical contact with eachother, although such physical contact can be present.

Young's modulus is a well-known physical parameter that is also known asthe elastic modulus, and is a measure of the stiffness of a solidmaterial. It is a mechanical property of solid materials, and definesthe relationship between stress (force per unit area) and strain in theelastic deformation region of such solid materials. It can be measuredas the ratio of stress along an axis to the strain (ratio of deformationover initial length) along that axis in the range in which elasticbehavior is observed and where Hooke's law holds. It can be measuredusing known equipment and mathematical calculations.

As used herein, particle size is defined using the terms “d50” and “d90”that refer to equivalent spherical volume diameter of particles at the50% frequency and 90% frequency point of the volume weighted frequencydistribution of the particle size, respectively, and can be determinedusing a commercially available Horiba Ltd. LA-920 particle size analyzerand instructions. Particle sizing methods and terminology are discussedin NIST special Publication 960-1 entitled “Particle SizeCharacterization: NIST Recommended Practice Guide” and in NIST specialPublication 960-3 entitled “The Use of Nomenclature in DispersionScience and Technology—NIST Recommended Practice Guide.” All datapresented below is based on volume weighted frequency distributions andthe equivalent spherical diameter model. The differences in the particlesize distributions of particles will be discussed herein using themedian spherical volume diameter of the typical particle sizedistributions shown in FIGS. 21-24 described below. The medianequivalent spherical volume diameter, Dv50, of the particle sizedistribution has units of length (for example, nanometers ormicrometers). The median equivalent spherical volume diameter, Dv50, ofthe particle size distribution measured and described herein is usedinterchangeably with the notation “d50” or “d50”. The median sphericalvolume diameter, d50, also has units of length and in the volumeweighted frequency distributions measured has interchangeable units ofmicrometers, or μm.

As used herein, the term “polydispersity coefficient” refers to anumerical quantity describing the relative breadth of a particle sizedistribution that is calculated from the mean and the standard deviationof a particle size distribution. Polydisperse systems are described onpage 3 of NIST Special Publication 960-3 titled “The Use of Nomenclaturein Dispersion Science and Technology”. This publication defines apolydispersed system that is not monomodal and contains many differentparticle sizes as follows: “a system may be considered polydisperse ifless than 90% of the size distribution (that equals 1.645 σ, where σ isthe standard deviation of the size distribution) lies within 5% of theaverage or mean size of the particles, <d>”. The polydispersitycoefficient employed here is identical to the metric for polydispersitydescribed in NIST SP960-3 and is calculated using the following formula:

$\frac{1.645\sigma}{\left\langle d \right\rangle}$wherein <d> is taken as the mean value spherical equivalent volumediameter of the particle size distribution as determined by instrumentemployed for the particle size distribution measurement.

Unless otherwise indicated, “N” refers to Newtons.

Uses

There are various uses of the composite articles prepared according tothe present invention and their incorporation into piezoelectric devicesincluding but not limited to, ignitors for various burners; energyharvesters including those that harvest energy from animal or humanbodies or from vibrating machines; piezoelectric transformers; sensorssuch as for piezoelectric microphones and ultrasonic transducers;actuators; elements for detection and generation of sonar waves; devicesfor monitoring power; pressure sensors; and tactile sensor applications.

The following TABLE I presents a non-exhaustive list of sensors andapplications for the composite articles according to this invention.

TABLE I Sensor type and application Comments Acoustic wave detectionSensor element for construction of sensor microphones, particularlymicrophones that detect contact with a surface Ultrasonic detectorFrequency response as low as 1 Hz and greater sensor than 100 kHz;pick-up sensor for non- destructive testing with acoustic wavesHydrophone sensor Underwater acoustic sensing with sensitive flexibletransducers for example, tsunami detection, excellent acoustic impedancematch to water Sonar sensor Underwater imaging using mechanicallyflexible transducers with excellent acoustic impedance match to waterMedical instrumentation Enhanced sensitivity of for example, pressuresensors sensitive catheters, CPAP machines, and others Pedobarographysensor Force sensors with enhanced sensitivity for biomechanicalanalysis of gait, posture, and foot contours Medical echography Enhancedsensitivity for diagnostic imaging sensor with ultrasound devices Bloodpressure sensor High force sensitivity with potential forminiaturization Robotics sensor Artificial sensitive skin and forcesensors Pressure sensor Direct and indirect sensing of pressure anddistribution of pressure on surfaces Security devices Intruder detectionusing vibration and impact; and for example, keypads for keyless locksVibration sensors Direct and indirect detection of vibrations withoptional frequency selectivity Strain sensors Direct and indirectdetection of sudden strain with optional frequency selectivity Detectionof localization Failure analysis and impact imaging of impacts sensorAccelerometer sensor Miniaturized inertial and kinetic devices forsensing acceleration and acceleration direction Keyboard key touchEnhanced human touch sensitivity sensor Human touch force Enhanced humantouch sensitivity sensors/human tactile sensors Force sensing inEnhanced human touch sensitivity in 3D capacitive touch sensorscapacitive touch sensor applications Sport and leisure contact Forexample, a tennis court boundary line to sensor detect the impactlocation of tennis ball Electrical switches Force sensitivepiezoelectric voltage is used to as a switch signal for electricalcircuitry Force sensitive Force sensitive piezoelectric voltage is usedto transistors open and close the transistor gate MicrogeneratorElectrical power generated and stored is proportional to time integratedforceEC and EC-P Compositions

Chemical formulations or compositions used to design both dry ECL's anddry ECL-P's are now described. One or more of each or both types ofelectrically-conductive layers can be present in a composite articleaccording to the present invention. An electrically-conductivecomposition without (b) particles is known herein as an EC composition,while an electrically-conductive composition containing (b) particles isknown herein as an EC-P composition. Thus, an EC composition and an EC-Pcomposition, as well as dry ECL and dry ECL-P, differ at least in thatthe EC-P composition and dry ECL-P contain one or more types of (b)particles as described below, and the EC and dry ECL contain none ofsuch (b) particles. However, all other components and features ofcompositions and layers can be the same or different.

Such EC compositions and EC-P compositions can also be used to providediscontinuous co-planar patterned electrodes that are described in moredetail below.

Electrical conductivity of an EC composition or EC-P composition isnecessary for effective use with a piezoelectric material and in suchdevice. In other words, each composite article is designed to functionwith one or more dry “electrodes” derived from an EC composition or EC-Pcomposition.

In general, each type of electrically-conductive composition exhibits anelectrical resistivity, when applied and dried (or contiguouslyarranged) on an insulating substrate (such as glass reinforced epoxylaminate sheets (PCB)), of less than 10,000 ohms-cm, or less than 500ohms-cm, or even less than or equal to 150 ohms-cm.

According to the present invention, each useful EC-P compositionconsists essentially of the following three essential components for thepurposes of the invention: (a) one or more electrically-conductivematerials as defined below; one or more types of (b) particles asdefined below; and (c) one or more binders as defined below; andoptionally, (d) a solvent medium as defined below, all in the definedamounts to provide desired formulations of the inventive EC-Pcompositions. The definitions below will make clear that (a) and (c)could be the same material and that some precursors to (c) could actalso as (d).

In general, the EC-P compositions typically have a viscosity that isdesigned for an intended use or means of application to form a compositearticle. Such a viscosity can be readily determined for a givencombination of composition components and intended use by one skilled inthe art using the teaching provided herein. For example, the EC-Pcomposition viscosity can be designed for its optimal application to adry PL, as either a uniform layer or in a predetermined pattern, usingsuitable printing or coating means and apparatus including but notlimited to, inkjet printing, screen printing, gravure printing of anytype, precision fluid dispensing, or electrostatic spraying, usingequipment and procedures that would be readily apparent to one skilledin the art.

(a) Electrically-Conductive Materials:

The essential (a) electrically-conductive materials are generallymaterials with high charge mobility. They can be particulate ornon-particulate, polymeric or non-polymeric, organic or inorganic, solidor liquid, and mixtures of any or multiple types of these materials canbe present in a composition used to prepare an EC or EC-P composition.

In general, such (a) electrically-conductive materials exhibits anelectrical conductivity of at least 2×10⁻⁴ S/m as measured usingstandard techniques known in the art of electrical measurement. Theelectrical conductivity is the reciprocal of the electrical resistivityfor a material. When an electrically conductive material is coated on asubstrate as a film then the electrical resistance of the film can bemeasured using a 4-probe method to determine the sheet resistance of thefilm. Suitable 4 probe methods for measuring sheet resistance includelinear 4 probe methods where the current is passed between two outercontacts and the voltage generated by the current passing through thesample is measured by two additional contacts located between the outercontacts. The well-known Van der Pauw 4 probe method was used herein.The Van der Pauw 4 probe method can be used to measure the sheetresistance of uniform electrically conducting films where the areacovered by the film can have an arbitrary shape. The electricalresistivity of the film can be determined by dividing the sheetresistance by the thickness of the film. The film thickness can bemeasured by any suitable method including optical methods such asinterferometry or microscopy, or by other methods such as contactprofilometry. If mixtures of different types of (a)electrically-conductive materials are used in the composition, thecumulative mixture can exhibit the desired electrical conductivity.

For example, useful particulate (a) electrically-conductive materialsinclude but are not limited to, electrically-conductive metallicparticles, alloys, inorganic or organic metal complexes, or compositematerials, such as those comprising silver, gold, titanium, platinum,palladium, copper, nickel, iron, silver coated copper, silver coatednickel, indium, gallium and its alloys, and aluminum, various types orforms of electrically-conductive carbon including graphite, graphene,buckyballs, and single- or multi-walled nanotubes, which can be suppliedas dispersions, pastes, or colloidal suspensions of theelectrically-conductive metal or electrically-conductivemetal-containing particles. Pure metal flakes, fibers, or particles canbe used. Such particulate electrically-conductive metallic materials canbe of any desired shape or particle size but in most instances, theyhave a median equivalent spherical volume diameter of at least 1 nm andup to and including 1000 μm or of at least 1 μm and up to and including100 μm, or a median largest dimension of less than 100 μm.

In general, when the (a) electrically-conductive materials are inparticulate form as noted above, they have a polydispersity coefficientof less than or equal to 3, or less than or equal to 2, or even lessthan or equal to 1.2. For example, silver nanoparticles (describedbelow) that are useful as (a) electrically-conductive materials can havea polydispersity coefficient that is less than 1.2.

Electrically-conductive organic materials such aselectrically-conductive organic polymers can also be used, individuallyor in mixtures, as (a) electrically-conductive materials. Examples ofsuch electrically-conductive organic polymers include but are notlimited to, substituted or unsubstituted pyrrole-containing polymers,substituted or unsubstituted thiophene-containing polymers, andsubstituted or unsubstituted aniline-containing polymers such as thosedescribed in Cols. 9-10 of U.S. Pat. No. 7,850,814 (Majumdar et al.) andreferences noted therein, the disclosure of which patent is herebyincorporated herein by reference. One or more of theseelectrically-conductive organic polymers can also serve as a (d) bindermaterial as that is defined below so that in such embodiments, aseparate (d) binder material can be present or absent from the EC orEC-P composition when one or more electrically-conductive organicpolymers are present.

Another class of useful (a) electrically conducting materials arepolyelectrolytes that can be solids or liquids at ambient conditions andwhere the electrical conduction is primarily by anion and cationtransport. Polyelectrolyte electrically-conductive materials can easilybe combined with other (a) electrically-conductive materials describedherein.

Particularly useful (a) electrically-conductive materials includemetallic nanoparticles such as silver nanoparticles that can be preparedor purchased and used as aqueous dispersions. For example, U.S. Pat. No.8,828,275 (Wang et al.) and U.S. Pat. No. 9,085,699 (Wang et al.)describe procedures for preparing dispersions of silver nanoparticles,the disclosures of both of which are hereby incorporated herein byreference. A representative method for preparing a dispersion of silvernanoparticles for use as an (a) electrically-conductive materialaccording to the present invention is described below in ComparativeExample 1.

Other useful particulate (a) electrically-conductive materials includeelectrically conductive inks such as the silver nanoparticle-containing“inks” that are commercially available from NovaCentrix that wereincorporated into the EC compositions used below in Comparative Examples2-4.

Silver nanoparticles are useful in the practice of this invention as (a)electrically-conductive materials, and they can have a d50 of less thanor equal to 60 μm or of at least 1 nm and up to and including 230 nm,and a d90 of less than or equal to 500 μm or of less than or equal to300 μm.

As one skilled in the art would recognize, a mixture of (a)electrically-conductive materials can comprise one or moreelectrically-conductive organic polymers as well as one or more types ofelectrically-conductive metallic particles. For example, a usefulmixture can comprise a polythiophene material with silver nanoparticles,in suitable weight proportions. In such embodiments, the polythiophenematerial can also serve as a (d) binder material as such materials aredescribed below.

The amount of one or more (a) electrically-conductive materials in theEC or EC-P composition can be at least 2 weight % and up to andincluding 99 weight %, or at least 5 weight % and up to and including 80weight %, or more likely at least 60 weight % and up to and including 75weight %, based on the total weight of the composition (including bothsolids and liquids). The amount of (a) electrically-conductive materialsin an EC-P composition can be the same or different as in an ECcomposition due to the presence of the (b) particles in the EC-Pcomposition.

(b) Particles:

The essential (b) particles used in the practice of the presentinvention can be composed of various materials and have various shapesand size distribution. A critical feature is that the Young's modulus ofthe (b) particles used in the EC-P composition must be different fromthe Young's modulus of the (a) electrically-conductive materials by atleast 10% (±10% of this value), or more particularly by at least 20%(±20%). Typically, this means that the chemical composition of the (b)particles is also different from that of the (a) electrically-conductivematerials in the EC-P composition.

The (b) particles generally have a d50 of at least 500 nm and up to andincluding 500 or more typically of at least 1000 nm and up to andincluding 250 μm. The d50 value for spherical particles is of coursetheir median equivalent spherical volume diameter, but in mostinstances, the (b) particles are not perfectly spherical, even thoughthe d50 can be measured as described above. In many instances, the trued50 is not always known from commercial product information (such asphysical dimensions of various shaped materials). The (b) particle d50can be the same as or different from the d50 of particulate (a)electrically-conductive materials. In most embodiments, the respectived50 of particulate (a) electrically-conductive material and (b)particles differ by at least an order of magnitude and the d50 ofparticulate (a) electrically-conductive material can be significantlysmaller than the d50 of the (b) particle.

Moreover, the (b) particles used in the practice of this inventiongenerally have a polydispersity coefficient of less than or equal to 3,less than or equal to 1.5, or even less than or equal to 1.25.

The (b) particles can be composed of one or more polymeric materials(homopolymers or copolymers) and mixtures of different polymericparticles can be used if desired. Particles composed of elastomeric(compressible) polymers are useful as well as solid non-elastic(non-compressible) particles. They can be crosslinked ornon-crosslinked. In some embodiments, the (b) particles are cores-shellparticles that have a core that is comprised of a material (such as apolymer) that is different from the material (such as a polymer)comprising the shell.

Hollow polymeric particles are also useful. For example, microspheres(or “hollow beads”) can comprise a thermoplastic shell that is eitherhollow inside or encloses a hydrocarbon or low boiling liquid such asisopentane or isobutane. Particles of this type are available asEXPANCE® microspheres from Akzo Noble Industries. In addition, Dualiteand Micropearl polymeric microspheres are commercially available fromPierce and Stevens Corporation. Hollow plastic pigments can also beused.

The (b) particles can be completely solid (non-porous) or they can beporous with micropores or nanopores scattered throughout the particlevolume, including the particle surface. The pores can be discrete(non-connected) or interconnected to form a porous network. Usefulporous particles having discrete pores essentially within the particleand methods for making them are described for example in U.S. Pat. No.8,110,628 (Nair et al.), the disclosure of which is hereby incorporatedby reference.

In addition, the (b) particles can have the same or different chemicalcomposition or Young's modulus as the PL as described below.

The (b) particles can be electrically-conductive, semi-conductive, orinsulating (dielectric) as those terms are known in the art. Thus, the(b) particles can have the same or different electrical conductivity asthe (a) electrically-conductive materials present in the EC-Pcomposition as long as the respective Young's moduli are different.

Representative (b) particles are described in the various InventionExamples shown below and many useful (b) particles can be purchased froma variety of commercial sources or they can be prepared using knownprocedures and starting materials especially where the (b) particles arepolymeric in content.

The amount of (b) particles in an EC-P composition is generally greaterthan 0 volume % and up to and including 88 volume %, or more likely atleast 8 volume % and up to and including 50 volume %, all based on thetotal wet volume of the EC-P composition. The amount of (b) particlescan also be defined in a dry weight ratio with the (a)electrically-conductive materials, and this weight ratio of (b)particles to (a) electrically-conductive material is generally at least0.01:1 and up to and including 10:1 or more likely at least 0.05:1 andup to and including 7:1. It is to be understood that any of suchparticles or materials can have other incorporated materials that areincluded in this weight ratio, for example, when the (a)electrically-conductive materials are silver nanoparticles havingdispersing material attached to the nanoparticles.

In addition, the (b) particles can be surface modified using polymerbrushes or other means to facilitate use of the particles in the EC-Pcompositions. Graded modulus particles can be used where the particlehas a surface coating with a modulus that is different from the bulk ofthe particle to tune the mechanical properties of the particle undercompressive stress.

(c) Binder Materials:

Composite articles can be prepared according to the present invention tocomprise a dry ECL-P that can comprise one or more (c) binder materialsthat are typically soluble or dispersible in a (d) solvent mediumdescribed below. Without wishing to be bound by theory, it is thoughtthat the (c) binder materials are generally present to help film-formingcapability of the (a) electrically-conductive material in a dry ECL-P.Suitable (c) binder materials can also be added to the EC-P or ECcompositions to adjust the rheological properties for a given use.Additionally, (c) binder materials allow improvement of the mechanicaland electrical continuity of a friable ECL-P that otherwise wouldexhibit compromised electrical properties, poor mechanical robustness,and insufficient adhesion. Due to the minimal volume or weight percentof the included (c) binder, it is thought to have negligible effect ond₃₃.

Useful (c) binder materials are generally polymeric in nature, meaningthat they have a weight average molecule weight of at least 5,000 oreven at least 10,000. In most instances, the (c) binder material is apreformed polymeric material, meaning that it was purchased as apolymeric material or manufactured as such before incorporation into theEC-P composition. In many embodiments, the (c) binder materials are“non-electrically conductive” (or insulative), having a volumeelectrical conductivity, in dry form, of less than 10⁻⁴ S/m as measuredby 4 probe conductivity measurements.

While useful EC-P and EC compositions often include one or more (c)binder materials as described above, it also possible for compositearticles to be prepared to have a dry ECL-P from which the (c) bindermaterial is absent. Such dry ECL-P would thus be prepared from an EC-Pcomposition consisting essentially of an (a) electrically-conductivematerial, (b) particles, and a (d) solvent medium.

In other embodiments, as described above, certain (a)electrically-conductive materials can also serve as (c) a bindermaterial so that a separate non-electrically-conductive (c) bindermaterial is not included. The EC-P composition of Invention Example 21and the composite article of Invention Example 43 described belowillustrate such embodiments.

In yet other embodiments, the (c) non-electrically conductive bindermaterial is not a preformed polymer but comprises polymer precursormaterials added to the EC-P composition, and the EC-P composition can betreated in such a way that the polymer precursor materials areconverted, for example by polymerization, into a suitable polymeric (c)binder material. For example, monomeric materials (such as one or morepolyacrylate precursors or monomers) and polymerization initiators canbe incorporated into the EC-P composition to form a dry ECL-P, andpolymerization is carried out to form a polymeric (c) binder material.The precursor monomeric materials can be polymerized using heat or UV orvisible irradiation. The EC-P composition of Invention Example 20 andthe composite article of Invention Example 41 described below illustratesuch embodiments.

Useful polymeric materials that can be present as preformed (c)non-electrically conductive binder materials can be chosen from manyclasses of polymeric materials, and mixtures of polymeric materials ofdifferent classes can be used if desired. Representative polymericmaterials include but are not limited to, polyurethanes (including butnot limited to polyether polyurethanes, polyester polyurethanes, andpolycarbonate polyurethanes); acrylate polymers (including methacrylatepolymers) that typically are derived from one or more ethylenicallyunsaturated polymerizable (meth)acrylate monomers including esters ofacrylic or methacrylic acid, which can be homopolymers or copolymersderived using multiple monomers; polyvinyl acetals such as poly(vinylbutyral); vinylidene fluoride polymers and their copolymers; chlorinatedpolymers; polyethylene oxide; and radiation curable polymer systems,ionizing or otherwise, including but not limited to polymer precursorsto acrylate polymers and free radical initiators.

As one skilled in the art would appreciate, the (c) binder materials orpolymeric precursors can be thermally or photochemically curablematerials and curing can be achieved after the EC-P composition has beenapplied.

In general, one or more (c) non-electrically conductive binder materials(polymeric or non-polymeric) can be present in the EC-P composition inan amount of at least 0.05 weight % and up to and including 5 weight %,or at least 0.25 weight % and up to and including 3 weight %, based onthe total weight of the EC-P composition.

(d) Solvent Medium:

A solvent medium can be used to formulate the EC or EC-P compositionsand typically comprise one or more miscible solvents that do notadversely affect any of the other essential components provided therein,and in which those components can be readily dissolved or dispersed,with the exception of dissolving the (b) particles. In addition, thesolvent medium must be useful for the desired viscosity and applicationmeans to form a composite article. The solvent medium must be chosen sothat it can be removed (for example, evaporated) in a suitable manner inthe provision of a dry ECL, dry ECL-P, or dry DL-P. When a (d) solventmedium is present and one or more (c) binder materials are also present,the one or more (c) binder materials are generally dispersible orsoluble in the (d) solvent medium. As noted above, some precursors topolymeric (c) binder materials can be monomeric and polymerizable andthey can also be in liquid form and can serve as a (d) solvent mediumfor the EC-P (or EC) composition.

However, as would be readily apparent to a skilled worker whounderstands the teaching herein about the (b) particles, the (d) solventmedium and (b) particles must be chosen so that the (b) particles arenot dissolved to any appreciable extent in the (d) solvent medium.Otherwise, the inventive effect from the presence of the (b) particleswould be severely diminished or absent.

In some embodiments, the (d) solvent medium can comprise predominantlywater, or even all water, with the possible presence of one or morewater-miscible organic solvents. By “predominant,” it is meant that atleast 70 weight % of the total weight of all solvents is water in suchembodiments, for example, where the (a) electrically-conductive materialare insoluble in water. In other embodiments, the (d) solvent medium cancomprise one or more organic solvents, with or without the presence ofwater, and such useful organic solvents include but are not limited to,dimethyl formamide (DMF), dimethyl acetamide, isopropyl alcohol,toluene, dipropylene glycol methyl ether, ketones, alcohols, and ethers.

In the ECL-P compositions according to this invention, the amount of the(d) solvent medium can be less than 98 weight %, and more likely atleast 4 weight % and up to and including 90 weight %, or up to andincluding 40 weight %, all based on the total weight of the EC-Pcomposition (or EC composition).

Those skilled in the art of formulations will recognize that the weightpercent of (d) solvent medium is often used to adjust a formulation fora particular use. For example, the amount or type of aqueous or organicsolvents in the (d) solvent medium can be used to adjust the rheologicalproperties of the composition according to the present invention.

However, it would also be recognized by those skilled in the art offormulation that the amount of (d) solvent medium can also affect thephysical properties of the final EC-P composition (or EC composition).For example, the amount or type of (d) solvent medium can also be usedto promote adhesion as well as wetting if the EC-P composition (or ECcomposition) is coated onto a substrate to make a composite article.

In some embodiments, it has been found that the (d) solvent medium canbe predominantly non-aqueous in nature and comprise, for example, apolar organic solvent that improves substrate wettability like dimethylformamide (DMF).

Optional Addenda:

The EC-P compositions according to this invention can optionally includeaddenda that may help with keeping materials in solution or dispersion,with application operations (such as coating or printing operations), orwith adhesion, and substrate wettability. Such materials can include butare not limited to surfactants, biocides, fungicides, viscositymodifiers, defoamers, humectants, anti-corrosion agents, anti-oxidants,radical scavengers, UV stabilizers, co-solvents, chelating agents,plasticizer, dehydration agents, and ionic strength control agents, eachin a suitable amount that would be readily determined from routineexperimentation or as recommended by commercial vendors. These optionaladdenda would be included at the minimum effective amounts to providethe necessary function but insufficient to negatively disrupt thenecessary electrical continuity of the dry ECL-P. As such optionalmaterials are optional, they could be left out as not being essential tothe performance of the essential (a), (b), and (c) binder materials (andin some embodiments, the (d) solvent medium) described above.

Making EC-P and EC Compositions:

To make suitable EC-P compositions according to the present invention,the (a) electrically-conductive material, (b) particles, and optional(c) binder material, can be mixed or dispersed within a suitable (d)solvent medium (or liquid precursors to (c) binder materials) usingeffective dispersion or stirring techniques and typically at roomtemperature. As noted above, it is essential that the (b) particles arenot dissolved in the (d) solvent medium of choice so the (b) particlesprovide their inventive effect in the resulting dried layers orpatterns. Representative details for making these compositions areprovided below in the working examples.

The (a) electrically-conductive material, (b) particles, and (c) bindermaterial if present, and suitable (d) solvent medium can be mixed usingany method familiar to those skilled in the art of mixing. In general,the EC-P compositions are prepared by first measuring out theappropriate amount of the (a) electrically-conductive material, (b)particles, and (c) binder material if present, and suitable (d) solventmedium if present. Measuring appropriate amounts of the (a), (b), (c),and (d) components can be accomplished by known methods in the artincluding measuring by volume or measuring by weight. The measuredamounts are mixed so that the (a) electrically-conductive material, (b)particles, and (c) binder material if present, and suitable (d) solventmedium are comingled. Mixing methods include the use of planetarymixers, paddle mixers, centrifugal mixers, stator-rotator mixers,sonication, static mixers, roller mills, 3 roll mills, or any other typeof mixer used for preparing mixed compositions. Those skilled in the artof mixing will recognize that composition formulations are frequentlyadjusted to optimize the uniformity of the mixed composition. Thecomingled (a) electrically-conductive material, (b) particles, (c)binder material, and (d) solvent medium if present, is contained in asuitable container before use. This container may or may not be the samecontainer used to mix or form the composition.

In the case of EC-P compositions where the (c) binder material is not apreformed polymer, but include precursor materials that are reactedafter deposition by any means of radiation curing known to those skilledin the art of radiation cured polymer systems, the factors of heat andradiation exposure must be considered during the compositionpreparation. It is critical to avoid premature initiation ofcrosslinking, photocuring, or thermal curing, whether by controlling thetemperature of the composition for thermally initiated processes oravoiding electromagnetic radiation exposure until the appropriate anddesired time to form the dry ECL-P.

As one skilled in the art would understand and as demonstrated belowwith the Comparative Examples, an EC composition can be prepared in thesame fashion as an EC-P composition but the (b) particles are omitted.The amounts and types of (a) electrically-conductive materials, (d)solvent medium, and (c) binder material, if present, can be determinedusing routine experimentation and the teaching about such materialsprovided herein.

In some embodiments, a dry dielectric layer (dry DL-P) containing (b)particles can be used in place of or in addition to a dry ECL-P toachieve the desired improved piezoelectric effect according to thepresent invention. To obtain a suitable dry DL-P, a D-P composition isformulated similarly to an EC-P composition. In such D-P compositionsand dry DL-P's, the (a) electrically-conductive materials describedabove are not present, and the resulting dry DL-P has a volumeconductivity that is less than 10⁻⁴ S/m, or even less than 10⁻¹⁰ S/m, asmeasured by 4 probe resistance methods.

Thus, a D-P composition consists essentially of one or more (a′)dielectric materials, (b) particles as described above for the EC-Pcompositions, and a (d) solvent medium as described above for the EC-Pcompositions.

In such embodiments, the (b) particles used in a D-P composition alsohave a Young's modulus that is different from the Young's modulus of the(a′) dielectric material(s) by at least 10%, or even at least 20%.

(a′) Dielectric materials can be used singly or in combination, and canbe particulate in form or film-forming polymers. For example, theessential (a′) dielectric materials can include, but are not limited to,both organic and inorganic polymers, sol-gel formulations, metal oxideframework solids, siloxanes, silicones, elastomeric materials of alltypes, including natural rubber, and Alcryn® polymer alloys,polyurethane polymers, engineering polyimide containing polymers such asPEEK and Kapton, and interpenetrating networks, as well as inorganicmaterials like talc and micaceous materials. It may be useful in manyembodiments, for at least some of the dielectric material to bepolymeric in nature to provide a “binder” or matrix for the (b)particles.

The amount of one or more (a′) dielectric materials in the D-Pcomposition is generally at least 5 weight % and up to and including 99weight %, or even at least 1 weight % and up to and including 95 weight%, based on the total D-P composition weight.

The amount of (b) particles in the D-P composition is generally greaterthan 0 volume % and up to and including 88 volume %, or more likely atleast 8 volume % and up to and including 50 volume %, all based on thetotal wet volume of the D-P composition. The amount of (b) particles canalso be defined in a dry weight ratio with the (a′) dielectricmaterials, and this weight ratio of (b) particles to (a′) dielectricmaterial is generally at least 0.01:1 and up to and including 10:1 ormore likely at least 0.05:1 and up to and including 7:1.

The (d) solvent medium used in the D-P composition can comprise one ormore suitable solvents in which the (a′) dielectric materials and anyadditional (c) binder material can be dissolved or dispersed and appliedto a suitable substrate (described below). As noted, the (d) solventmedium must be chosen so that the (b) particles are not dissolved, andan appropriate choice of one or more solvents would be readily apparentto a skilled worker in the art using routine experimentation and aknowledge of the solubility of various materials in water or organicsolvents, or mixture thereof. For example, some useful organic solventsthat can be used in a (d) solvent medium for a D-P composition includebut are not limited to, isopropyl alcohol, toluene, n-methylpyrrolidinone, dimethyl formamide (DMF), alcohols, ketones, and ethers.

In the D-P compositions according to this invention, the amount of the(d) solvent medium is generally less than 90 weight %, and more likelyat least 4 weight % and up to and including 90 weight %, or up to andincluding 40 weight %, all based on the total weight of the D-Pcomposition.

Those skilled in the art of formulations would recognize that the weightpercent of (d) solvent medium is often used to adjust a formulation fora particular use. For example, the amount or type of aqueous or organicsolvents in the (d) solvent medium can be used to adjust the rheologicalproperties of the D-P composition according to the present invention.

However, it would also be recognized by those skilled in the art offormulation that the amount of (d) solvent medium can also affect thephysical properties of the final D-P composition or dry DL-P. Forexample, the amount or type of (d) solvent medium can also be used topromote adhesion as well as wetting if the D-P composition is coatedonto a substrate to make a composite article.

Piezoelectric Materials

All known piezoelectric materials are dielectric materials. Dielectricmaterials have low electrical conductivity (<10⁻⁶ S/m) and theirconductivity remains low even at elevated voltages until the reducedelectric field provided by the voltage is sufficient to cause electricalarcing through the material, at which point the material becomeselectrically conducting. Thus, dielectric materials have thecharacteristic of becoming electrically conducting at what is known inthe art as a “breakdown voltage.” Within the class of materials that arepiezoelectric in nature there is a subset of materials that also exhibitpyroelectricity. A pyroelectric material will exhibit temperatureinduced polarization that can be measured as a voltage and the degree ofpolarization varies with temperature. Within the subset of materialsthat exhibit pyroelectricity there is another subset of materials thatalso exhibit ferroelectricity. Ferroelectric materials also exhibitpolarization that can be measured as a voltage and additionally thepolarization that is reversibly affected by application of an electricfield. All ferroelectric materials are also piezoelectric and allpyroelectric materials are also piezoelectric. The present invention isapplicable to piezoelectric materials and all pyroelectric and allferroelectric, and such materials can be provided in a dry PL asdescribed herein.

Piezoelectric materials that can be used in the practice of the presentinvention are generally known in the art and include known singlecrystalline ceramics, polycrystalline ceramics, polymer-polycrystalline,polymer-nanocrystalline composites, and polymeric materials havingpiezoelectric properties, that is, they exhibit a measurablepiezoelectric effect as that property is known in the art. Somepiezoelectric materials are found in nature, but for most industrialapplications, synthetic ceramics or polymers are formed into suitablepiezoelectric materials such as blocks, machined shapes, sheets, andfilms.

Many useful synthetic piezoelectric ceramic materials arepolycrystalline materials whose crystal structure is associated withnon-centrosymmetric space groups. Such piezoelectric materials include,but are not limited to, lead zirconate titanate (PZT), barium titanate,potassium niobate, sodium tungstate, sodium potassium niobate, bismuthtitanate, sodium bismuth titanate, bismuth ferrite, materials possessingwurtzite structures like ZnO, GaN, InN, and AlN. Non-crystallinedielectrics as well as non-centrosymmetric and centrosymmetriccrystalline materials can also exhibit polarization effects uponapplication of external force. Ceramics often exhibit higher d₃₃piezoelectric charge coefficients than polymer systems. However, thesematerials tend to be brittle.

It would also be apparent to one skilled in the art that compositearticles and devices could be prepared using the teaching provided toinclude flexoelectric materials.

Synthetic polymeric materials are well known in the art of piezoelectricmaterials and include but are not limited to poly(vinylidene fluoride)(PVDF); copolymers derived in part from PVDF; blends of PVDF with otherpolymers; polyamides; polyureas; polyethylene oxide; polylactic acid;polyhydroxybutyrate; parylene-C; liquid crystalline polymers; and othersdescribed in Khaled S Ramadan et al 2014 Smart Mater. Struct. 23 033001.The piezoelectric behavior of these materials is often associated withspecific phases of the polymer matrix. The beta phase of PVDF is aparticularly useful phase of PVDF for observing the piezoelectriceffect. Moreover, the beta phase of PVDF is both pyroelectric andferroelectric. These materials tend to be flexible and exhibit a lowerd₃₃ piezoelectric charge coefficient than polycrystalline or crystallinepiezoelectric materials.

Both crystalline materials and polymeric materials exhibitingpiezoelectric, pyroelectric, and ferroelectric behavior can be formed orshaped into any particularly useful form as part of the compositearticles according to the present invention. Such materials can be usedin the form of sheets or films, or they can be applied or otherwisedisposed on a substrate of some type and secured using an adhesive ifdesired, for example as described and illustrated in FIGS. 14 and 15 ofU.S. Pat. No. 6,469,421 (noted above), the disclosure of which isincorporated herein by reference.

Composite Articles (with Either Dry ECL-P or Dry DL-P)

In their simplest form (or structure), composite articles according tothe present invention can have only two essential components: (1) a drypiezoelectric layer (dry PL) comprising a piezoelectric material asdescribed above, and having first and second opposing surfaces; andeither (2) one or more dry electrically-conductive layers (dry ECL-P's)or one or more dry dielectric layers (dry DL-P's), arranged contiguouslywith at least one of the first and second opposing surfaces of the dryPL. Each of the dry ECL-P's is prepared from an EC-P composition asdescribed above, each of the dry ECUs can be prepared from an ECcomposition as described above, and each of the dry DL-P's is preparedfrom a D-P composition as described above. Unless otherwise specified,the discussion herein about dry PL, dry ECL, dry ECL-P, dry DL-P, andnon-electrically-connected co-planar patterned electrodes is meant torefer to respective dry layers or patterned electrodes containinglimited solvent(s), or less than 5 weight %, based on the total weightof the respective layer or patterned electrode.

Each dry ECL-P consists essentially of one or more (a)electrically-conductive materials, one or more types of (b) particles,and optionally, one or more (c) binder materials, all as describedabove. Each dry DL-P consists essentially of one or more (a′) dielectricmaterials, one or more types of (b) particles, and optionally, one ormore (c) binder materials, all as described above.

A composite article can also include a dry electrically-conductive layer(dry ECL) formed from an electrically-conductive composition (EC) thatdoes not contain (b) particles as described above. Like the dry ECL-P, adry ECL can serve as an electrode in a composite article, or within adevice containing a composite article.

The opposing surfaces of a piezoelectric layer can be planar ornon-planar.

In some embodiments, multiple electrodes prepared from an EC compositionor EC-P composition are in contact with and adjacent to the same planaror curved surface but they are not in electrical communication with eachother. These electrodes (usually in the form of one or more pairs ofelectrodes) are considered co-planar in that they are adjacent to thesame single surface (single planar or curved surface), for example of asingle surface of a dry PL, but they are not electrically (orphysically) connected or in contact with each other. For example, a dryECL or dry ECL-P can be used to provide non-electrically-connectedco-planar patterned electrodes contiguous with the same surface whereinone or more of such electrodes is derived from an EC-P. In otherembodiments, a dry ECL and dry ECL-P that are in contact with andoverlaying the same single planar or curved surface can be in electricalcommunication with each other.

A dry ECL can also be formed from an electrically-conductive metallicfilm that has been deposited by any method readily apparent to thoseskilled in the art. For example, such metallic films can be deposited byelectrochemical deposition, electroless deposition, or deposition fromthe vapor phase by means of physical vapor deposition, sputtering, oratomic layer deposition. Representative electrically-conductivematerials include, but are not limited to, alloys, inorganic or organicmetal complexes, or composite materials, such as those comprisingsilver, gold, nickel, platinum, palladium, copper, nickel, iron,titanium, silver coated copper, silver coated nickel, indium, galliumand its alloys, and aluminum as well as various electrically-conductiveforms of carbon including graphite, graphene, buckyballs, andsingle-walled or multi-walled nanotubes, any of which can be depositedas electrically-conductive materials to form a dry ECL.

The (a) electrically-conductive materials useful in the dry ECL or dryECL-P can be crystalline, polycrystalline, or amorphous, and they can beordered or disordered. Further examples of such electrically-conductivematerials are described above.

The amounts of essential and optional components in the dry ECL-P or dryDL-P can differ from the respective weight percentages described abovefor the wet EC-P composition or D-P composition, respectively.

For example, the one or more (a) electrically-conductive materials canbe present in the dry ECL-P in an amount of at least 2 weight % and upto and including 99 weight %, or at least 20 weight % and up to andincluding 97 weight %, all based on the total dry weight of the dryECL-P. The amount of the (b) particles in the dry ECL-P can bedetermined as a dry weight ratio to the one or more (a)electrically-conductive materials of at least 0.01:1 and up to andincluding 10:1, or more typically of at least 0.03:1 and up to andincluding 7:1.

As noted above, some (a) electrically-conductive materials can act as(c) binder materials. However, where a separate (c) binder material isused, it can be present in the dry ECL-P in an amount of at least 0.05weight % and up to and including 20 weight %, or at least 0.1 weight %and up to and including 5 weight %, based on the total weight of the dryECL-P. The dry ECL-P can also include any optional addenda incorporatedinto the EC-P composition as described above.

Moreover, each dry ECL-P is designed so that when it is arranged indirect contact with or adjacent to an insulating substrate (such as adielectric layer on a support), it can exhibit an electrical resistivityof less than 10,000 ohms-cm or of less than 500 ohms-cm, or even of lessthan 150 ohms-cm.

For a dry DL-P, the amount of one or more (a′) dielectric materials isgenerally at least 5 weight % and up to and including 99 weight %, or atleast 10 weight % and up to and including 95 weight %, all based on thetotal dry weight of the dry DL-P. The amount of the (b) particles in thedry DL-P can be determined as a dry weight ratio to the one or more (a′)dielectric materials of at least 0.01:1 and up to and including 10:1, ormore typically of at least 0.03:1 and up to and including 7:1. Theoptional (c) binder material can be present in the DL-P in an amount ofat least 0.1 weight % and up to and including 10 weight %, or at least0.1 weight % and up to and including 5 weight %, based on the total dryweight of the dry DL-P. The dry DL-P can also include any optionaladdenda incorporated into the dry ECL-P as described above.

A composite article according to the present invention can be providedin any desirable and practical form or shape including flat structures,continuous webs, molded or cast shapes, shapes containing concavesurfaces, shapes containing convex surfaces, as well as spherical shapesas long as there is at least one dry ECL-P or dry DL-P can becontiguously arranged or disposed on (generally directly adjacent to) asurface of a dry PL. In some embodiments, the composite article has aflat or planar structure or shape. In other embodiments, the compositearticle has a non-planar structure or shape and can be in the form of acylindrical rod, a cone-like shape, a shape containing one or morepolyhedral figures, or other complex shapes containing one or morecurved surfaces.

Optional components of a composite article that are not a dry ECL-P, dryECL, dry DL-P or dry PL include but are not limited to substrates,protective dry overcoat layers, and adhesive layers that help maintainstructural integrity during manufacture or use.

A composite article according to the present invention can be composedof a single dry ECL-P disposed on or arranged contiguously to oneopposing surface of a dry PL, and that opposing surface can be planar ornon-planar. Alternatively, two individual dry ECL-P's can be disposed onand arranged contiguously with both opposing surfaces of the dry PL. Inother embodiments, two individual non-electrically-connected co-planarpatterned electrodes (described below) that are not in electricalcommunication with each other can be disposed on or arrangedcontiguously to same one or both opposing surfaces of a dry PL.

In the previous and following discussion of composite articlescomprising a dry PL and at least one dry ECL-P, unless otherwisespecified, it is to be understood that similar embodiments according tothe present invention can be designed in which a dry DL-P is used inplace of one or more dry ECL-P's that are present. Thus, it iscontemplated that composite articles according to this invention canhave at least one dry DL-P and no dry ECL-P's (but perhaps at least onedry ECL), at least one dry ECL-P and no dry DL-P's (with or without adry ECL), or at least one dry DL-P and at least one dry ECL-P (with orwithout a dry ECL), along with the essential dry PL.

Without wishing to be bound by theory, the relationship between the sizeof the (b) particles in the dry ECL-P and the dry thickness of a dryECL-P, is now described for the embodiment of a dry ECL-P with a uniformand random distribution of (b) particles throughout its volume. It is tobe understood that random and uniform distribution of the (b) particlesthroughout the layer is thought to be desirable, but it is also possiblethat the (b) particle distribution is non-random or non-uniform.

A first dimensionless variable, κ_(ECL-P), is defined as the ratio ofthe dry thickness of the dry ECL-P in units of micrometers to d50(micrometers) of the (b) particles in the dry ECL-P. A seconddimensionless variable, ϕ, or volume fraction, is defined as the volumefraction of (b) particles and is related to the weight % of thecomponents (a), (b), and (c) through the dry density of each component.A third dimensionless variable, Δ_(M), is defined as the ratio of thevalue of any mechanical property of the (a) electrically-conductivematerial to the value of the same mechanical property of the (b)particles in the dry ECL-P. The variable Δ_(M) can be the ratio of theYoung's modulus for the (a) electrically-conductive material to theYoung's modulus of the (b) particles in the dry ECL-P. Similarly, Δ_(M)can also be the ratio of the hardness of the (a) electrically-conductivematerial to the hardness of the (b) particles in the dry ECL-P. Ingeneral, Δ_(M) is not equal to 1 and more likely, Δ_(M) is less than 0.9or greater than 1.10. Alternatively, it is desirable that at least onemechanical property of the (a) electrically-conductive material in thedry ECL-P differs from the same mechanical property of the (b) particlesin the dry ECL-P by 5% or more. For example, the hardness of the ceramicmicrobeads used in Invention Examples 25 through 27 is reported by themanufacturer to be 6 on the MOHS scale, corresponding to roughly 9-10GPa on the indentation Vicker's scale. The measured correspondingnanoindentation hardness of the electrically-conductive silvernanoparticles in the same Invention Examples is roughly 0.2+0.07 GPa.The modulus of the electrically-conductive silver nanoparticles is 2% ofthe modulus of the ceramic microbeads and therefore the modulus of theelectrically-conductive silver nanoparticles is approximately 98%different from that of the ceramic microbeads. Thus, Δ_(M) in theseembodiments is approximately 0.02, which is less than 0.9.

Also, without wishing to be bound by theory, the dimensionless variableκ_(ECL-P), is now discussed with respect to the volume fraction ofparticles, ϕ, in the dry ECL-P for embodiments where Δ_(M) is smallerthan 0.8 or greater than 1.2 for the purpose of describing how thegeneration of non-uniform stress in the ECL-P is affected by bothκ_(ECL-P) and ϕ during application of uniform force onto the dry ECL-P.This non-uniform stress generated in the dry ECL-P is propagated intothe PL and may be affected by the dry ECL-P itself and by anyintermediate layers between the dry ECL-P and the dry PL such as anintermediate dry ECL. It is assumed that the (b) particles in dry ECL-Phave different mechanical properties than the (a) electricallyconductive material in the dry ECL-P and this difference is expressed bya third dimensionless variable Δ_(M). κ_(ECL-P), ϕ, and Δ_(M) aredimensionless variables that relate to non-uniform stress generation inthe composite articles comprised of a dry ECL-P and a dry PL. Thefollowing TABLE II illustrates the qualitative relationship betweenκ_(ECL-P), ϕ, and creation of non-uniform stress in the dry PL duringforce application to the dry ECL-P for cases where the mechanicalproperties of the (a) electrically conducting material in the dry ECL-Pand the same mechanical property for the (b) particles in the dry ECL-Pare sufficiently mismatched such that Δ_(M) is smaller than 0.8 orgreater than 1.2.

TABLE II ϕ is small ϕ is large κ_(ECL-P) is small Non-uniform stress isNon-uniform stress is small large κ_(ECL-P) is large Non-uniform stressis Non-uniform stress is small small

When κ_(ECL-P) is large and the volume fraction of particles, ϕ, inECL-P is small, the (b) particles comprise a small part of the totalvolume of the ECL-P and the creation of non-uniform stress byapplication of force on the ECL-P is minimized. Similarly, whenκ_(ECL-P) is large, the volume fraction of (b) particles, ϕ, in ECL-Papproaches 1, then the (b) particles comprise a large part of the totalvolume of the ECL-P and the creation of non-uniform stress byapplication of force on the ECL-P is minimized. This effect is due to3-dimensional (b) particle jamming.

When κ_(ECL-P) is small, the volume fraction of (b) particles, ϕ, inECL-P is small, the (b) particles comprise a portion of the total volumeof the ECL-P and the creation of non-uniform stress by application offorce on the ECL-P is large.

When κ_(ECL-P) is small, the volume fraction of (b) particles, ϕ, in adry ECL-P is large, the (b) particles comprise nearly all the volume ofthe dry ECL-P and the creation of non-uniform stress by application offorce on the dry ECL-P is minimized because of two and three-dimensional(b) particle jamming. The generation of non-uniform stress in the dryECL-P is best accomplished when the volume fraction of (b) particles inthe dry ECL-P is below the volume fraction above which (b) particlejamming occurs. For (b) particles that are approximately spherical isshape, three-dimensional (b) particle jamming occurs approximately above64 volume % (b) particles. Thus, for spherical (b) particles in the dryECL-P, the volume fraction, ϕ, of (b) particles in the dry ECL-P layershould be below 64% (or 0.64 of a total volume=1). The three-dimensional(b) particle jamming limit will change depending on the shape of the (b)particles in the dry ECL-P.

There are many different combinations of the three dimensionlessvariables κ_(ECL-P), ϕ, and Δ_(M) that can be used to producenon-uniform stress in the dry ECL-P during force application. Anotherdimensionless variable, κ_(PL), can be defined as the ratio of the drythickness of the dry PL in units of micrometers to d50 in micrometers ofthe (b) particles in the dry ECL-P. When κ_(ECL-P) is very large, thenon-uniformity of stress from the dry ECL-P that is applied to the dryPL in the presence of an applied force is minimized. Under theseconditions, regardless of value of κ_(PL), the piezoelectric response ofthe dry PL is not strongly affected by non-uniform stress and the drythickness of the dry PL does not affect the piezoelectric response ofthe composite. κ_(PL) is important when κ_(ECL-P) is small. For a smallvalue of κ_(ECL-P) non-uniform stress is generated at the surface of thedry PL when a force is applied to the dry ECL-P largely by means of (b)particles proximate to the dry PL surface. When κ_(PL) is small then alarge portion the dry PL dry thickness or even the entire dry PL drythickness is exposed to the non-uniform stress field. Comparison of thed₃₃ piezoelectric charge coefficients and calculated ratios of compositearticles designed for, for example, Invention Example 26 and InventionExample 43, both of which were coated with the dry EC-P composition ofInvention Example 5 suggest that a smaller κ_(PL) gives rise to improvedpiezoelectric response for the same dry ECL-P. The comparison of thecomposite articles of Invention Examples 26 and 43 suggests that thestress giving rise to the piezoelectric response is affected by the dryPL dry thickness.

A useful range for the dry thickness of the dry ECL-P is at least 1 μmand up to and including 1500 μm, or at least 5 μm and up to andincluding 200 μm. A useful range for the dry thickness of the dry PL isat least 1 μm and up to and including 1500 μm, or at least 10 μm and upto and including 250 μm. Those skilled in the art will recognize thatthe dry PL can have a thickness much greater than 1500 μm when thepiezoelectric material is a polycrystalline ceramic and particularlywhen the dry PL shape is complex. A suitable d50 for (b) particles inthe dry ECL-P is at least 1 μm and up to and including 1500 μm, or atleast 5 μm and up to and including 200 μm.

A dry DL-P can have the same or different dry dimensions as a dry ECL-Pand the (b) particles can be of the same or different size as describedfor a dry ECL-P.

The present invention is now described by referring to various compositearticles illustrated in FIGS. 1 to 19 in which FIG. 1 shows a typicalprior art composite article while FIGS. 2-19 show various embodiments ofcomposite articles that can be designed and used according to thepresent invention.

Thus, in FIG. 1, prior art composite article 10 comprises dry ECL 20that is arranged contiguously with an opposing surface of dry PL 30.

In FIG. 2, composite article 15 comprises dry ECL-P 25 containingmultiple (b) particles 35, which is arranged contiguously with anopposing surface of dry PL 30.

Another embodiment according to the present invention is illustrated inFIG. 3 in which composite article 40 comprises dry ECL-P 25 containingmultiple (b) particles 35, which is arranged contiguously with a firstopposing surface of dry PL 30; and dry ECL 20 that is arrangedcontiguously with a second opposing surface of dry PL 30.

Still another useful embodiment according to the present invention isillustrated in FIG. 4 in which composite article 45 comprises first dryECL-P 25 containing multiple (b) particles 35, which is arrangedcontiguously with a first opposing surface of dry PL 30; dry ECL 20 thatis arranged contiguously with a second opposing surface of dry PL 30;and second dry ECL-P 50 containing multiple (b) particles 55 that can bethe same or different from multiple (b) particles 35, and which seconddry ECL-P 50 is arranged contiguously with a surface of dry ECL 20.

FIG. 5 describes composite article 60 that comprises first dry ECL-P 25containing multiple (b) particles 35, which is arranged contiguouslywith a first opposing surface of dry PL 30; and second dry ECL-P 50containing multiple (b) particles 55 that can be the same or differentfrom multiple (b) particles 35, and which second dry ECL-P 50 isarranged contiguously with a second opposing surface of dry PL 30.

Moreover, in FIG. 6, composite article 65 comprises first dry ECL-P 25containing multiple (b) particles 35, which is arranged contiguouslywith a first opposing surface of dry PL 30; second dry ECL-P 50containing multiple (b) particles 55 that can be the same or differentfrom multiple (b) particles 35, and which second dry ECL-P 50 isarranged contiguously with a second opposing surface of dry PL 30; anddry ECL 20 that is arranged contiguously with a surface of second dryECL-P 50.

In FIG. 7, composite article 70 comprises dry ECL-P 25 containingmultiple (b) particles 35, which is arranged contiguously with anopposing surface of dry PL 30; and dry ECL 20 that is arrangedcontiguously with a surface of dry ECL-P 25.

In FIG. 8, composite article 75 comprises dry ECL-P 25 containingmultiple (b) particles 35, which is arranged contiguously with anopposing surface of dry PL 30; dry ECL 20 that is arranged contiguouslywith dry ECL-P 25; and second dry ECL 80 that is arranged contiguouslywith a second opposing surface of dry PL 30.

FIG. 9 illustrates composite article 85 that comprises dry ECL-P 25containing multiple (b) particles 35, which is arranged contiguous to aplanar surface of dry PL 30; dry ECL 20 that is arranged contiguous todry ECL-P 25; second dry ECL 80 arranged contiguously with a secondopposing surface of dry PL 30; and second dry ECL-P 50 containingmultiple (b) particles 55 that can be the same or different frommultiple (b) particles 35, which is arranged contiguously to a surfaceof second dry ECL 80.

Another embodiment according to the present invention is illustrated inFIG. 10 in which composite article 95 comprises dry ECL-P 25 containingmultiple (b) particles 35, which is arranged contiguously to an opposingsurface of dry PL 30; dry ECL 20 that is arranged contiguously to asurface of dry ECL-P 25; second dry ECL-P 50 containing multiple (b)particles 55 that are the same or different from multiple (b) particles35, which is arranged contiguously with a second opposing surface of dryPL 30; and second dry ECL 80 that is arranged contiguously with asurface of second dry ECL-P 50.

FIG. 11 illustrates yet another embodiment according to the presentinvention in which composite article 100 comprises dry ECL 20 that isarranged contiguously with an opposing surface of dry PL 30; and dryECL-P 25 containing multiple (b) particles 35, which is arrangedcontiguously with a surface of dry ECL 20.

FIG. 12 illustrates composite article 105 that comprises dry ECL 20 thatis arranged contiguously with an opposing surface of dry PL 30; dryECL-P 25 containing multiple (b) particles 35, which is arrangedcontiguously with dry ECL 20; and second dry ECL 80 that is arrangedcontiguously with a second opposing surface of dry PL 30.

Composite article 110 illustrated in FIG. 13 is similar to thatillustrated in FIG. 12 except that it further comprises second dry ECL-P50 containing multiple (b) particles 55 that are the same or differentfrom multiple (b) particles 35, which is arranged contiguously with asurface of second dry ECL 80.

Those skilled in the art of piezoelectric materials will appreciate thatcontiguously arranged dry ECL's and dry ECL-P's may or may not be inelectrical communication with each other. Dry ECL's and dry ECL-P's onopposing surfaces of a dry PL are generally not in electricalcommunication with each other except by means of an external circuitused to collect charge or voltage from dry ECL's and dry ECL-P's onopposing surfaces of the dry PL.

FIG. 14 illustrates composite article 125 that is like composite article15 shown in FIG. 2, but which further comprises outermost dry protectivelayer 130 that is disposed over dry ECL-P 25 that is arrangedcontiguously with an opposing surface of dry PL 30. Outermost dryprotective layer 130 can be opaque or transparent, and it can beelectrically conductive or non-electrically conductive (thus, insulativeor dielectric). In some embodiments, outermost dry protective layer 130can be a polymeric protective layer. In other embodiments, outermost dryprotective layer 130 can be comprised of essentially inorganicmaterials. In yet other embodiments, outermost dry protective layer 130can be comprised of a mixture of inorganic and organic materials.

In general, an outermost dry protective layer can be arranged ordisposed over any composite article according to the present inventionincluding, but not limited to, those represented in FIGS. 2-13, 15, and16.

Desirable characteristics of an outermost dry protective layer include,but are not limited to, flexibility, chemical inertness, mechanicaldurability, scuff resistance, providing a suitable form factor for theapplication, and manufacturability. Mechanical durability is a desirablecharacteristic of an outermost dry protective layer to prevent itscracking during use. Flexibility of the outermost dry protective layeris desirable to allow adequate propagation of stress through it to thedry ECL-P and the dry PL in the composite article. It is desirable thatthe outermost dry protective layer possess a certain amount ofelasticity to ensure that enough stress is propagated through thevarious (b) particle-containing layer(s) to the dry PL so that chargecan be generated from the externally applied force. In some embodiments,the outermost dry protective layer can be mechanically hard with a highmodulus and brittle. In addition, chemical inertness is desirable toprotect the underlying layers from corrosion and other forms of chemicalattack of the composite article. It is additionally desirable thatoutermost dry protective layer possess a low water permeability toprevent excessive water absorption in the composite article becausewater absorption can interfere with the performance of the dry PL. It isfurther desirable that the outermost dry protective layer be scuffresistant and protect the composite article from scratches,fingerprints, and other damage that can occur during manufacture,transport, and use. The materials used to form an outermost dryprotective layer are generally determined by its intended design andpurpose.

The dry thickness of an outermost dry protective layer can be at least 5nm and up to and including 5 mm. In some embodiments, the thickness ofthe outermost dry protective layer can be at least 5 nm and up to andincluding 25 nm as is common for self-assembled monolayer films.Self-assembled monolayers may be applied as an outermost dry protectivelayer by any means known to those skilled the art of fabrication ofself-assembled monolayers. Such methods include, but are not limited to,deposition of self-assembled monolayers from both the liquid and vaporphase as well as slot coating, spin coating, atomic layer deposition,molecular beam epitaxy, physical vapor deposition, dip coating, andother methods readily apparent to those skilled in the art.Fluoropolymer self-assembled monolayers are often well suited forpreparing hydrophobic surfaces and low surface energy surfaces with lowcoefficients of friction and stiction (static friction) that aids in thephysical release of two surfaces after contact. Parylene monolayers areoften well suited for preparing hydrophobic surfaces with low waterpermeability.

In other embodiments, the thickness of an outermost dry protective layercan be at least 500 nm and up to and including 5,000 μm as is common forpolymer or composite layers. Useful polymeric materials for this purposecan include both organic polymers, inorganic polymers, organometallicpolymers, and a mixture of such classes of polymers. Representativepolymeric materials include, but are not limited to, resins, urethanes,polyesters, nylons, polyolefins including polypropylenes, polyethylenesand polybutylene polymers, polystyrenes, acrylates, polycarbonates,cellulose, imides, polyetherketones, fluoropolymers, chloropolymers,epoxides, vinyl chlorides, cross-linked polymers, interpenetratingpolymer networks, and other types of polymers including elastomers suchas neoprenes, nitrile butyl rubbers, chlorosulfonated polyethylenes,terpolymers and others. Useful inorganic polymer materials include, butare not limited to, organometallic polymers such as silicones,polysiloxanes, and polyphosphazenes. Useful addenda to include in anoutermost dry protective layer include antioxidant compounds as well asUV absorbing substances and dyes like TINUVIN® light stabilizercompounds, organic and inorganic particulates and nanoparticulatesuseful for improving abrasion resistance and surface hydrophobicity.

Polymeric materials can be applied to form an outermost dry protectivelayer by any means known to those skilled the art of fabrication ofpolymeric material layers. Such methods include, but are not limited to,solvent casting, spin coating, dip coating, spray coating, brushcoating, extrusion, slot coating, curtain coating, electrospraying,lamination, physical vapor deposition, in-situ chemical polymerization,photopolymerization, thermal polymerization, molding including injectionmolding, electrodeposition, precision liquid dispensing including heatand radiation curing methods, gravure and flexographic methods forforming continuous films, screen printing, drop-on-demand ink jetprinting, continuous inkjet printing, and other methods familiar tothose skilled in the art of fabrication of polymeric films.

In other embodiments, the dry thickness of an outermost dry protectivelayer can be at least 500 μm and up to and including 5,000 μm as iscommon for fabricated, laminated, or machined layers.

In still other embodiments, an outermost dry protective layer can becomprised of a hard, stiff material having a dry thickness of at least50 μm and up to and including 5,000 μm with a high elastic modulus sothat a non-uniform force impinging thereon is spread out over itssurface area due to its high elastic modulus, thereby resulting inmechanical stimulation of a larger area of the underlying dry PL andminimizing the possibility that the dry PL is subjected to a localizedforce that exceeds its compressive strength. Examples of hard, stiffmaterials with high elastic modulus that are useful for this purposeinclude but are not limited to, metal alloys of all types includingaluminum alloys and steel alloys, compressed graphite, metal nitrides,metal carbides, engineering plastics like nylons, liquid crystallinepolymers, polyetherketone polymers and their copolymers, polyimidepolymers and their copolymers, diamond, silicon and its alloys,engineering composites such as fiberglass and carbon fiber filled-epoxycomposites of all types, inorganic and organic glasses, high modulusceramics, glasses, and glass ceramics of all types including aluminumoxide based ceramics, alumino-silicate based ceramics, zirconium oxidebased ceramics, aluminum nitride based ceramics, silicate basedceramics, and others readily apparent to one skilled in the art.

A high elastic modulus outermost dry protective layer can be fabricatedby any method known in the art for fabricating high modulus materials.Such methods include metallurgical methods such as melting and forming,hydroforming, electrodeposition, electroforming, molding, injectionmolding, deposition methods of all types including those describedabove, polishing, grinding, machining, electropolishing, and slipcasting. It is recognized that when a high modulus outermost dryprotective layer is fabricated as a separate piece, it can beadvantageous to employ an adhesive layer to attach it so that it issuitably disposed in a composite article. The adhesive layer used forthis purpose is not shown in FIG. 14 but it could be located directlybetween outermost dry protective layer 130 and dry ECL-P 25.

It is also recognized that in an alternate embodiment, an outermost dryprotective layer, regardless of the material of construction, can beadvantageously disposed relative to the other layers without therequirements that it be contiguous with a dry ECL-P in the manner shownin FIG. 14. For example, an outermost dry protective layer can beadvantageously disposed proximate to but not in physical contact withdry ECL-P 25 that is arranged contiguously with an opposing surface ofdry PL 30 in FIG. 14.

A dry PL and at least one dry ECL-P can be disposed on a substrate in acomposite article, which substrate does not participate in electricalactivity, and such layers can be arranged on one or both supportingsurfaces of such substrate, with or without an adhesive. Usefulsubstrate materials include, but are not limited to, ceramics, polymersand plastics of all types, silicon, glasses of all types, metals of alltypes including metals and alloys of high elastic modulus, paper andcellulosic materials, composites of all types including fiberglass andcarbon fiber composites, concrete compounds of all types, laminatedstructures, and corrugated structures. The substrate can be the same ordifferent in size or dry thickness as one or all layers disposedthereon.

FIG. 15 illustrates composite article 135 in which dry PL 30 is arrangedon substrate 140 and first dry ECL-P 25 containing multiple (b)particles 35 is arranged contiguously with an opposing surface of dry PL30 and second dry ECL-P 50 containing multiple (b) particles 55 (thatare the same or different from multiple (b) particles 35) is arrangedcontiguously with substrate 140 and to a second opposing surface of dryPL 30. In one embodiment of composite article 135, first dry ECL-P 25and the second dry ECL-P 50 are optically transparent or substantiallytransparent, permitting 50% or more, at least 75%, or at least 90% ofvisible wavelengths of light. Dry PL 30 is a transparent orsubstantially transparent material, as in the case of PVDF and substrate140 is transparent or substantially transparent. Substrate materialsinclude but are not limited to glass, PET, PEN, and cellulose acetate.Materials in the dry ECL-P's are index matched to one another and to dryPL 30 in one embodiment. Index matching refers to two materials havingthe same index of refraction so when light passes through the materialsreflection and refraction do not occur. In another embodiment, thepattern of the dry ECL-P allows for minimal light scattering and lowabsorption through dry ECL-P's 25 and 50. The pattern comprises anoptically opaque material and is sufficiently thin in a directionperpendicular to the thickness direction of the dry ECL-P that it is notimmediately noticeable to the human eye. In another embodiment, a dryECL is substituted for one of the dry ECL-P's and this dry ECL isoptically transparent. Optically transparent conductive materialsinclude but are not limited to, indium tin oxide, indium zinc oxide, andthin films of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate.

In composite article 145 illustrated in FIG. 16, dry ECL-P 25 containingmultiple (b) particles 35 is arranged contiguously with a surface ofsecond dry ECL-P 50 that contains multiple (b) particles 55, which isarranged contiguously with an opposing surface of dry PL 30. Multiple(b) particles 55 can be the same or different as multiple (b) particles35, either in content (amount) or composition.

Composite article 145 in FIG. 16 can be further modified to provide adry ECL in any suitable location, such as between dry ECL-P 25 andsecond dry ECL-P 50; arranged contiguously with the outer surface of dryECL-P 25; between dry ECL-P 50 and dry PL 30; or arranged contiguouslywith the second opposing surface of dry PL 30.

FIGS. 17-19 illustrate several embodiments of composite articlesaccording to the present invention in which at least one dry DL-P ispresent. While FIGS. 17-19 are illustrative of only three specificembodiments, other embodiments would be readily apparent from discussionprovided herein.

In FIG. 17, composite article 90 is similar to that shown in FIG. 2, butit has dry DL-P 150 containing a dielectric material and (b) particles35, which is arranged contiguously with an opposing surface of dry PL30.

FIG. 18 illustrates yet another embodiment in which composite article115 has dry DL-P 150 containing a dielectric material and (b) particles35, which is arranged contiguously with a surface of dry ECL 20 that inturn is arranged contiguously with an opposing surface of dry PL 30.

Still another embodiment is illustrated in FIG. 19 in which compositearticle 120 has dry DL-P 150 containing (b) particles 35 is arrangedcontiguously with one opposing surface of dry PL 30 and second dry DL-P155 containing (b) particles 55 is arranged contiguously with a secondopposing surface of dry PL 30. Dry ECL 20 is arranged contiguously witha surface of second dry DL-P 155.

Another embodiment using a DL-P composition is similar to FIG. 15 with adry DL-P contiguously with one opposing surface of dry PL 30 and with adry ECL or dry ECL-P arranged contiguously with a second opposingsurface of dry PL 30. The dry DL-P is arranged contiguously withsubstrate 140 or the dry ECL or dry ECL-P is arranged contiguously withsubstrate 140. In this embodiment, the dry DL-P, the dry PL, the dry ECLor dry ECL-P, and the substrate are optically transparent orsufficiently transparent, that is transmitting at least 50%, or at least75%, or still at least 90% of visible wavelengths of light. The dry DL-Pis made using optically transparent materials and index matching adielectric material to the (b) particles in the dry DL-P. The dielectricmaterial and the (b) particles have the same index of refraction.

Inventive Devices Containing Composite Articles

The composite articles described according to the present invention canbe incorporated into various useful devices as generally describedabove. There are many types of piezoelectric devices. Those skilled inthe art of device design using piezoelectric materials for the purposeof employing the charge generating properties of the piezoelectriccharge coefficient like d₃₃ are familiar with the two force-sensitivepiezoelectric devices: 1) devices that are designed so that thepiezoelectric material (or dry FL) is exposed directly to an appliedforce in order to generate a piezoelectric response; and 2) devices thatare designed so that the piezoelectric material (or PL) is exposedindirectly to an applied force in order to generate a piezoelectricresponse. These two types of piezoelectric devices are also known askinetic force devices (or kinetic piezoelectric devices) and inertialforce devices (or inertial piezoelectric devices), respectively. Forexample, a piezoelectric crystal that is directly strained by forceapplication to produce a voltage for spark formation is a kineticpiezoelectric device because the piezoelectric material (or dry PL) isdirectly exposed to an applied force. For example, a cantilever beamtype energy harvester with a dry PL that is part of the beam is aninertial piezoelectric device because an inertial force is generated onthe cantilever beam when an external force is applied to the beamsupport structure and the dry PL is stressed by the inertial force ofthe oscillating beam.

FIG. 30a illustrates electromechanical model 159 for devices containingpiezoelectric materials. Spring 160, dashpot 165, and piezoelectricmaterial 170 (such as a dry PL) are in common mechanical communicationwith support 175. Piezoelectric material 170 can be provided in a dry PLof a composite article according to the present invention that alsocomprises at least two electrodes 180. The assembly of piezoelectricmaterial 170 with at least two electrodes 180 according to the presentinvention further comprises electrical communications means attached toboth the first and second electrodes for electrical communication of thecomposite article with an external electrical circuit is a piezoelectriccapacitor. Mass 185 is in mechanical communication with spring 160,dashpot 165, and piezoelectric material 170 such that they allexperience the same applied force from mass 185 or when mass 185 has aforce applied to it. In FIG. 30a , piezoelectric material 170 iscontiguous to electrodes 180 that are connected to external electricalcircuit load 190. According to the present invention, at least one ofelectrodes 180 is a dry ECL-P. If piezoelectric material 170 requirespoling, it can be poled at any desired orientation relative toelectrodes 180. External electrical circuit load 190 is desirablyimpedance matched to piezoelectric material 170 with electrodes 180 andcan provide a variety of functions including but not limited to signalprocessing of the voltage, current, or charge produced by piezoelectricmaterial 170 under applied stress or storage of charge produced bypiezoelectric material 170 under applied stress. Those familiar withgeneralized electromechanical models will recognize and appreciate thatspring 160 represents the lumped elastic behavior of all componentshaving elastic behavior in a composite article according to the presentinvention (that can compose electrodes 180 and piezoelectric material170); dashpot 165 represents the lumped viscous mechanical behavior ofall materials having viscous behavior in the composite article thatresist motion by means of viscous friction, and piezoelectric material170 represents the lumped piezoelectric properties and response of allpiezoelectric materials present in a PL of the composite article.

FIG. 30b is an electromechanical diagram of kinetic (or kinematic)piezoelectric device 195 in which a composite article according to thepresent invention containing piezoelectric material 170 in a dry PL andelectrodes 180 is incorporated and at least one of electrodes 180 is adry ECL-P according to this invention. FIG. 30b illustrates the use ofelectromechanical model 159 of FIG. 30a to describe a piezoelectricresponse of kinetic piezoelectric device 195 with the characteristics ofelectromechanical model 159 in the presence of direct applied force 200.Kinetic piezoelectric device 195, like all kinetic piezoelectricdevices, is provided with a means to transmit all or a portion of anapplied force directly to a piezoelectric material. The piezoelectricresponse of piezoelectric material 170 or of a composite articlecontaining same to direct applied force 200 from mass 185 or applied tomass 185 is also known as the direct response, the kinetic response, orthe kinematic response of kinetic piezoelectric device 195. Mass 185 isalso called a proof mass. Mass 185 provides a means for transmitting allor a portion of applied force 200 to piezoelectric material 170. When anacceleration is applied to mass 185, the force as a function of timethat is applied to piezoelectric material 170 is affected by the elasticproperties represented by spring 160 and the viscous propertiesrepresented by dashpot 165 that are present, and piezoelectric material170 is exposed to compressive or tensile stress depending on theorientation of direct applied force 200 relative to surfaces ofpiezoelectric material 170. The direct piezoelectric response producedby the piezoelectric material 170 from direct applied force 200 ismeasured as power, voltage, or current charge in coulombs by externalelectrical circuit load 190, is proportional to direct applied force200, and follows the profile of direct applied force 200 as a functionof time. In one embodiment, direct applied force 200 is compressive innature. In another embodiment, direct applied force 200 is tensile innature. Alternatively, direct applied force 200 can oscillate betweentensile and compressive natures.

FIG. 30c is an electromechanical diagram of inertial piezoelectricdevice 205 and illustrates the use of electromechanical model 159 shownin FIG. 30a to describe a piezoelectric response of inertialpiezoelectric device 205 with the characteristics of electromechanicalmodel 159 in FIG. 30a in the presence of secondary inertial appliedforce 210. The inertial piezoelectric response of piezoelectric material170 (such as a dry PL in a composite article) or of an inertialpiezoelectric device containing piezoelectric material 170 to secondaryinertial applied force 210 is also known as inertial response orindirect response. Inertial piezoelectric device 205, like all inertialpiezoelectric devices, is provided with a means to convert all or aportion of an applied force to an inertial force that is transmitted toa piezoelectric material. FIG. 30c shows that electromechanical model159 shown in FIG. 30a that includes mass 185, spring 160 representingthe lumped elastic behavior present, dashpot 165 representing the lumpedviscous behavior present, piezoelectric material 170 representing thelumped piezoelectric behavior and support 175 are in common mechanicalcommunication with a mechanical assembly 215 in an inertial fashion sothat direct applied force 200 exerted on mechanical assembly 215produces secondary inertial applied force 210 on mass 185 and also onspring 160, dashpot 165, and piezoelectric material 170. Mechanicalassembly 215 provides a means to convert all or a portion of directapplied force 200 to inertial applied force 210 that is transmitted topiezoelectric material 170. Mechanical assembly 215 is shown in FIG. 30cas a box-like enclosure to which support 175 shown in FIG. 30a ismechanically attached so that there is mechanical communication withinmechanical assembly 215. When direct applied force 200 is applied tomechanical assembly 215, secondary inertial applied force 210 is appliedto mass 185 in an opposite direction to direct applied force 200.Secondary inertial applied force 210 is applied to mass 185 as well asto spring 160, dashpot 165, and piezoelectric material 170, and theforce as a function of time that is applied to piezoelectric material170 is a function of the lumped elastic and lumped viscous propertiespresent. The piezoelectric response of piezoelectric material 170 tosecondary inertial applied force 210 is measured as power, voltage,current, or surface charge by the external load 190 and is proportionalto secondary inertial applied force 210. The piezoelectric response isout of phase with the expected piezo response that would be produced bythe profile of direct applied force 200 as a function of time becausesecondary inertial applied force 210 is roughly 180 degrees out of phasewith direct applied force 200.

Those familiar with charge generating piezoelectric materials understandthat piezoelectric materials (for example, in a dry PL) can havemultiple piezoelectric charge coefficients that are directionallydependent and that the response contribution of each directionalpiezoelectric charge coefficient is dependent on the magnitude of theappropriate force vector component that is contributed by the appliedforce on the dry PL. Without wishing to be bound by theory, thedescriptions of inventive devices provided herein are generaldescriptions of how the dry PL (for example, in a composite article)interacts with externally applied forces with respect to any givenpiezoelectric charge coefficient that contributes to the response of thedry PL. In general, the dry PL response is related to the magnitude ofthe individual contributions from each piezoelectric charge coefficientas well as the directional orientation of the externally applied force.Those skilled in the art of physics would recognize that the externallyapplied force on a kinematic or inertial piezoelectric device (asillustrated in FIGS. 30b and 30c , respectively) can be described interms of the sum of all the vector components of the force in eachdirection of a defined reference frame. It is convenient to define onedirection of a reference frame for describing applied force, kinematicor inertial, as the direction of the largest active piezoelectric chargecoefficient of the dry PL. The externally applied force or inertialapplied force can have any desired directional orientation relative tothe orientation of the piezoelectric charge coefficients of the dry PL.In some kinematic piezoelectric devices, the applied force has a vectorcomponent that is parallel to the largest active piezoelectric chargecoefficient of the dry PL. In other kinematic piezoelectric devices, theapplied force has a vector component that is not parallel to the largestactive piezoelectric charge coefficient of the dry PL. In some inertialpiezoelectric devices, the inertial force has a vector component that isparallel to the largest active piezoelectric charge coefficient of thedry PL. In other inertial piezoelectric devices, the inertial force hasa vector component that is not parallel to the largest activepiezoelectric charge coefficient of the dry PL.

FIGS. 31a-31c illustrate three embodiments of the incorporation and useof an inventive composite article in both kinetic (or kinematic) andinertial piezoelectric devices. FIG. 31a shows composite article 135according to the present invention and as illustrated in FIG. 15 (seefor respective composite article components) with mass 185 arrangedcontiguously with one of electrodes that would be dry ECL-P 25.Composite article 135 can be arranged contiguously with and uniformlyattached to mass 185 on the chosen opposing, contiguous attachmentsurfaces so that the kinetic force produced by an acceleration appliedto mass 185 produces stress that is uniformly distributed over thecontact area between the surface of mass 185 and the outer surface ofdry ECL-P 25 of composite article 135.

The kinetic (or kinematic) piezoelectric device embodiment shown in FIG.31a can function as a kinetic piezoelectric device when substrate 140 ofcomposite article 135 is fixed and stationary and an accelerationtowards or away from it is applied to mass 185. An example of anacceleration of mass 185 towards substrate 140 would be a finger pushingon the opposing outer surface of mass 185. The piezoelectric response ofdry PL 30 in response to the applied force from mass 185 is measured byexternal electrical circuit load 190 as power, voltage, or currentcharge in coulombs, is proportional to the applied force, and followsthe profile of the applied force as a function of time. Alternatively,an inertial device using composite article 135 shown in FIG. 31a canfunction as an inertial piezoelectric device when substrate 140 isnon-stationary and not fixed and is accelerated towards or away frommass 185. In this case, mass 185 reacts in an inertial manner andproduces an inertial force on dry PL 30 that is opposite the force andacceleration of substrate 140. The piezoelectric response of dry PL 30in response to the applied force from mass 185 is measured by externalelectrical circuit load 190 as power, voltage, or current charge incoulombs, is proportional to the applied force, follows the profile ofthe applied force as a function of time, and is 180 degrees out of phaserelative to the kinetic embodiment illustrated in FIG. 31 a.

In another embodiment, in the kinetic (kinematic) piezoelectric deviceillustrated according to FIG. 31a , dry PL 30 responds directly toapplied force and composite article 135 is uniformly attached to asurface of mass 185 that is accelerated for force generation in morethan one location to enable the force application over the entiresurface of composite article 135.

In yet another embodiment (not shown), an inertial device illustratedaccording to FIG. 31a , dry PL 30 responds to an inertial force, andcomposite article 135 is uniformly attached to a surface of mass 185that is accelerated for force generation in more than one locationthereby enabling the force application uniformly over the entire surfaceof composite article 135.

The inertial device embodiment of FIG. 31a where dry PL 30 responds toan inertial force, the composite article 135 according to the presentinvention and containing at least one dry ECL-P is uniformly attached inmore than one location to surface substrate 140 that is accelerated togenerate inertial force so that the force application over the sensingsurface of composite article 135 is uniform.

FIG. 31b shows an embodiment of inertial piezoelectric device 220wherein composite article 135 is used as a cantilever beam. Substrate140 of composite article 135 is laterally extended so that substrate 140extends beyond dry ECL-P/dry PL/dry ECL-P layer stack (25/30/50 inorder) in both lateral directions. One laterally extended side ofsubstrate 140 is in mechanical communication with a clamping mechanism(not shown) and is held in a stationary fashion. Tip mass 225 isattached to the opposing lateral extension of substrate 140 such thatthe dry ECL-P/dry PL/dry ECL-P layer stack (25/30/50 in order) ispositioned between tip mass 225 and the clamping mechanism (not shown).Tip mass 225 is in mechanical communication with the clamping mechanism(not shown) by means of substrate 140 of composite article 135 and isheld stationary on support means 230.

Alternately, substrate 140 can be laterally extended in one directionand clamped while tip mass 225 is attached directly to the opposingsurface of dry ECL-P 25 of composite article 135 at a desired locationthat can be near the unclamped end of substrate 140. Tip mass 225 is inmechanical communication with the clamping mechanism (not shown) bymeans of composite article substrate 140. The application of a primaryforce to the clamping mechanism (not shown) results in the applicationof an opposing inertial force from tip mass 225 on composite article135. Any means known in the art may be employed for application of aprimary force to the clamping mechanism (not shown) to produce anopposing inertial force from tip mass 225 on composite article 135. DryPL 30 of composite article 135 generates a piezoelectric response in thepresence of the inertial force. The piezoelectric response iselectrically communicated to external electrical load circuit 190. Thepiezoelectric response of dry PL 30 in response to the inertial forcefrom tip mass 225 is measured by the external electrical load circuit190 as power, voltage, or current charge in coulombs, and isproportional to the primary applied force. Those skilled in the art ofinertial piezoelectric devices of the cantilever beam type wouldrecognize that a variety of beam shapes and sizes are possible and thatthe inertial force response of the inertial piezoelectric device 220increases as the primary force becomes periodic and the frequency ofprimary force oscillations drives the cantilever beam of the inertialpiezoelectric device 220 into mechanical resonance. Those skilled in theart of cantilever beam design would know that to a first approximation,the frequency of mechanical resonance of a cantilever beam can bedetermined by variables including, but not exclusively limited to, thelength of the beam, the cross-sectional area of the beam, the effectivemoment of inertia of the beam, the effective modulus of the beam, andthe effective density of the material of construction of the beam.

The cantilever beam can have two or more dry piezoelectric layers (dryPL's) and two or more dry ECL-P's. The cantilever beam can be comprisedof a composite article and the opposing side of a substrate. In anotherembodiment, the cantilever beam can be a unimorph beam. In yet anotherembodiment, the cantilever beam is a bimorph. For example, thecantilever beam can be comprised of a dry ECL or dry ECL-P, a dry PL,another dry ECL or dry ECL-P, a dry PL, and yet another dry ECL or dryECL-P wherein the poling directions of the dry PL's are oriented so theyare opposite.

FIG. 31c illustrates inertial piezoelectric device 235 wherein compositearticle 135 is in the shape of a plate or disc and is radially extendedso that it extends the dry ECL-P/dry PL/dry ECL-P layer stack (25/30/50in order) in a radial fashion uniformly in all radial lateraldirections. Composite article 135 can be in mechanical communicationwith clamping mechanism support 240 and is held in a stationary fashionso that the edges of the disc shaped composite article 135 are clampedin at least one location around its circumference.

In another embodiment, the radially extended dry ECL-P/dry PL/dry ECL-Player stack can be contiguous with a substrate (not shown) that is inmechanical communication with clamping mechanism support 240 and is heldin a stationary fashion so that the edges of the disc-shaped compositearticle 135 are clamped to clamping mechanism support 240 in at leastone location around its circumference.

Alternatively, the disc-shaped composite article 130 can be clamped atmultiple locations around its circumference. Clamping mechanism support240 can be any suitable mechanical means. Alternatively, clamping can beachieved by adhesive means. Still again, clamping can be achieved byboth mechanical and adhesive means. Clamping mechanism support 240 inFIG. 31c can have a cylindrical hollow shape that allows compositearticle 135 to vibrate as a supported membrane in a drum-like fashion.For example, clamping mechanism support 240 can be closed at one end,closed at both ends, or open at both ends.

Clamping mechanism support 240 can be comprised of a piezoelectricmaterial, or can be comprised of a dry PL and a dry ECL. In anotherembodiment, clamping mechanism support 240 can be comprised of a dry PLand a dry ECL-P. A tip mass (not shown in FIG. 31c ) can be contiguouswith and attached to an opposing surface of disc-shaped compositearticle 135. For example, it can be attached to an opposing surface ofdisc-shaped composite article 135 at its center. In yet anotherembodiment, the tip mass can be attached to an opposing surface of dryECL-P 25 of a dry ECL-P/dry PL/dry ECL-P layer stack (25/30/50 inorder). Moreover, the tip mass can be attached to the opposing surfaceof substrate (not shown) of composite article 135. The tip mass can alsobe in mechanical communication with a clamped disc shaped compositearticle (not shown). The application of a primary force to clampingmechanism support 240 results in the application of an opposing inertialforce from an inertial tip mass on composite article 135. Dry PL 30 incomposite article 135 generates a piezoelectric response in the presenceof the opposing inertial force. The piezoelectric response iselectrically communicated to external electrical load circuit 190. Thepiezoelectric response of dry PL 30 in response to the inertial forcefrom an inertial tip mass is measured by external load circuit 190 aspower, voltage, or current surface charge in coulombs, and isproportional to the primary applied force. Those skilled in the art ofinertial piezoelectric devices of the plate type would recognize that avariety of plate shapes and sizes are possible and that the inertialforce response of inertial piezoelectric device 235 can increase as theprimary force becomes periodic and the frequency of primary forceapplication drives the clamped composite article 135 into mechanicalresonance. Those skilled in the art of plate design and plate resonancewould know that to a first approximation, the frequency of mechanicalresonance of a circular membrane or a circular plate is determined byvariables including but not limited to the radius of the plate, thecross-sectional area of the plate, the effective modulus of the plate,and the effective density of the material of construction of the plate.

Thus, FIGS. 30a, 30b, and 30c show electromechanical models for bothkinetic and inertial piezoelectric devices and FIGS. 31a, 31b, and 31cshow exemplary device designs for both kinetic and inertialpiezoelectric devices, all of which devices can comprise a compositearticle according to the present invention. These illustrations areexemplary and not limiting or restrictive in scope. Other device designsare possible and fall within the scope of kinetic and inertialpiezoelectric devices according to the present invention. All theembodiments of piezoelectric device designs discussed herein employ theproperties of the piezoelectric charge coefficients d₃₃ and d₃₁.However, it is recognized that kinetic and inertial piezoelectricdevices that utilize additional piezoelectric charge coefficients arepossible and, in some cases, desirable.

Those skilled in the art of device design utilizing piezoelectric chargecoefficients of piezoelectric layers would understand that the responsemeasured by an electrical measurement circuit in electricalcommunication with a dry PL is affected by the impedance matching of theelectrical circuit load to the impedance of the dry PL. There are manyequivalent circuit models in the art of piezoelectric materials that areused to represent piezoelectric elements for impedance matching of anexternal electrical circuit.

Without wishing to be bound by theory, it is thought that one of thesimplest electrical models of a dry PL that is stressed by a force togenerate surface charge is an adjustable voltage source, the voltage ofwhich varies with applied force, that is in series with a capacitor.This can be most easily understood when it is considered that apiezoelectric material itself is a dielectric with a large dielectricconstant that is positioned between two electrodes further comprising ameans for electrically communicating to an external electrical circuitas is customary with the construction of a capacitor.

A piezoelectric capacitor according to the present invention isillustrated in FIG. 32a in which piezoelectric capacitor 245 comprises acomposite article comprising dry PL 30, dry ECL-P 25 containing (b)particles 35 which acts as a first electrode and is contiguous with onesurface of dry PL 30, and second dry ECL-P 50 containing (b) particles55 which acts as a second electrode and is contiguous with the opposingsurface of dry PL 30. Piezoelectric capacitor 245 is similar inconstruction as composite article 60 shown in FIG. 5. Piezoelectriccapacitor 245 also comprises electrical communication means 250 forelectrically communicating with an external circuit (not shown) forexample that can be wire leads that are attached to dry ECL-P 25 and dryECL-P 50 by any means known in the art of electrical connection. The (b)particles 35 can be the same or different from (b) particles 55 indensity, distribution (amount), or composition.

Various other inventive piezoelectric capacitors can be designed asshown in FIGS. 4, 6, 9, 10, 13, 15, 16, 39-42, 45, and 46.

In another embodiment, piezoelectric capacitor 245 is shown in FIG. 32b, comprising dry DL-P 150 containing (b) particles 35 which iscontiguous with dry ECL 20 that is contiguous with one surface of dry PL30. Contiguous with the opposite surface of dry PL 30 is dry ECL-P 50containing (b) particles 55. Alternatively, to this embodiment, a seconddry ECL can be used in place of dry ECL-P 50. Piezoelectric capacitor245 has electrical communication means 250 for electricallycommunicating with an external circuit (not shown) for example that canbe wire leads or electrically-conductive ribbons that are attached todry ECL 20 and dry ECL-P 50.

Still another embodiment shown in FIG. 32c , is piezoelectric capacitor245 in which dry DL-P 150 comprising (b) particles 35 is contiguous withone surface of dry PL 30 and is also contiguous with dry ECL 20.Contiguous with the opposite surface of dry PL 30 is dry ECL-P 50comprising (b) particles 55.

Those familiar with art of piezoelectric device design and electricalmeasurement know that the measurement of capacitance, resistance,voltage, and impedance are important for device application. Theresistance across a piezoelectric capacitor can be measured byconnecting a high impedance resistance measuring circuit between the twoelectrodes. The capacitance across a piezoelectric capacitor can bemeasured at a chosen frequency by connecting a capacitance measuringcircuit between the two electrodes. The impedance across a piezoelectriccapacitor can be measured by connecting an impedance measuring circuitbetween the two electrodes, and the impedance can be determined by theresistance of the layer and the capacitance of the layer. The voltageacross a piezoelectric capacitor can be measured by connecting a highimpedance voltage measuring device between the two electrodes. Thosefamiliar with measuring piezoelectric devices know that in the absenceof charge leakage, the voltage across a piezoelectric capacitor measuredby a high impedance voltage measuring device is related to the forceapplied to the dry PL and the surface charge that is generated thereby.Charge leakage causes the piezo responsive voltage to degrade anddisappear over time. Additionally, those skilled in the art ofelectrical design recognize that electrical power losses are minimizedwhen impedances of the power source match the impedance of the load. Thepiezoelectric capacitor and the composite articles illustrated in FIGS.3-6, 8, 9, 12, 13, and 15 can act as power sources when a force isapplied to the piezoelectric capacitor or composite article when surfacecharge is generated thereby. Any external circuit in electricalcommunication with the electrodes of the piezoelectric capacitor can actas an electrical load. Thus, when the piezoelectric capacitor is inelectrical communication with an external circuit, it can beadvantageous to match the impedance of the external circuit to that ofthe piezoelectric device to maximize power transfer of the kineticpiezoelectric devices disclosed herein.

Impedance matching is useful to maximize power transfer of the inertialpiezoelectric devices disclosed herein. Any of a piezoelectriccapacitor, kinetic piezoelectric device, and inertial piezoelectricdevice, can be impedance matched to and in electrical communication withan external electrical circuit. Alternatively, any of a piezoelectriccapacitor, kinetic piezoelectric device, and inertial piezoelectricdevice, can be impedance mismatched to and in electrical communicationwith an external electrical circuit.

A wide variety of external electrical circuits that are useful formeasuring the electrical output of piezoelectric devices are known. Whenperiodic, oscillating forces are applied to a piezoelectric capacitor,or to a kinetic or inertial piezoelectric device, according to thepresent invention, the electrical output from the piezoelectriccapacitor is essentially bipolar, meaning that the voltage and currentvary in a periodic fashion between positive and negative values as afunction of time. Those skilled in the art of device design wouldrecognize that it is useful to rectify the alternating voltage orcurrent for storage of the generated energy or to produce a DC signalfor further analysis. In one embodiment, the kinetic and inertialpiezoelectric devices, or the piezoelectric capacitors, can be inelectrical communication with a means of current and voltagerectification.

For example, a means of current and voltage rectification illustrated inFIG. 33 can be used to rectify current and voltage from AC to DC in theform of a well-known diode bridge 255 comprised of four diodes 260, 265,270, and 275 that are arranged to produce a DC current or voltage. Theoperating principles of a diode bridge are well known and will not bediscussed here. A kinetic and inertial piezoelectric device, or apiezoelectric capacitor, can be in electrical communication with a meansof current and voltage rectification wherein the means of current andvoltage rectification is diode bridge 255.

The means of current and voltage rectification can be in electricalcommunication with a means of storing the rectified electrical energysuch as energy storage device 280 as shown in FIG. 33, that can be, forexample, a capacitor, a battery, or a supercapacitor. For example, therectified DC current or voltage from a rectifying circuit can be used tocharge a capacitive energy storage device to store the energy producedby a kinetic or inertial piezoelectric device. More than four diodes canbe used to construct the rectifying circuit that can include at leastone energy storage device 280 providing a means of storing electricalenergy, or that can include at least one means of releasing electricalenergy stored by energy storage device 280. For example, the rectifyingcircuit can include at least one means of releasing stored electricalenergy that is an electrical switch.

In another embodiment of a rectifying circuit, the use of diodes in theelectric circuits that are in electrical communication with an inertialand kinetic piezoelectric device is not required and electric circuitsthat employ other types of switches, inductors, and capacitors are knownin the art. The use of switchable capacitor banks to improve theimpedance matching between the output from the PL in inertial or kineticpiezoelectric devices and the electrical circuit is known in the art.The rectifying circuit can include at least one capacitor, at least oneresistor, at least one switch, or at least one inductor. The means ofstoring electrical energy can be in electrical communication with ameans of liberating electrical energy for application to a secondelectrical circuit.

The kinetic or inertial piezoelectric devices, or piezoelectriccapacitors according to this invention can be in electricalcommunication with a charge amplifier, the purpose of which is tomeasure the cumulative charge that is produced by the dry PL in adevice. The kinetic piezoelectric devices, inertial piezoelectricdevices, or piezoelectric capacitors, each having at least one dry ECL-Por dry DL-P according to the present invention, can be in electricalcommunication with a charge amplifier.

In another embodiment, a kinetic piezoelectric device, inertialpiezoelectric device, or piezoelectric capacitor, each having a dryECL-P or dry DL-P according to the present invention can be inelectrical communication with a high impedance voltage measuring circuitwhose purpose is to measure the voltage generated by surface charge thatis produced by the piezoelectric layer in the device.

A piezoelectric capacitor and a kinetic or inertial piezoelectric devicedesigned according to the present invention can have many practical usesas shown for example in TABLE III below that provides a non-exhaustive,non-limiting list of such uses. The first column of TABLE III indicatessensor type. The second column, titled “Kinetic,” is labeled with an “X”in the row of the sensor type to indicate that sensors of the typeindicated in column one can be designed using a kinetic piezoelectricdevice according to the present invention or a variant thereof. Thethird column, titled “Inertial”, is labeled with an “X” in the row ofthe sensor type to indicate that sensors of the type indicated in columnone can be designed using an inertial piezoelectric device of thepresent invention or a variant thereof.

TABLE III Sensor type and Use Kinetic Inertial Comments Acoustic wave XX Sensor element for construction detection sensor of microphones,particularly microphones that detect contact with a surface Ultrasonic XFrequency response as low as 1 Hz detector sensor and greater than 100kHz; Pick-up sensor for non-destructive testing with acoustic wavesHydrophone X Underwater acoustic sensing with sensor sensitive flexibletransducers for example tsunami detection, excellent acoustic impedancematch to water Sonar sensor X Underwater imaging using mechanicallyflexible transducers with excellent acoustic impedance match to waterMedical X X Devices with enhanced sensitivity instrumentation such aspressure sensitive sensors catheters, CPAP machines, and vibrationsensors to detect patient movements Pedobarography X Force sensors withenhanced sensor sensitivity for biomechanical analysis of gait, posture,and foot contours Medical X Enhanced sensitivity for echographydiagnostic imaging with sensor ultrasound devices Blood pressure X Highforce sensitivity with sensor potential for miniaturization Roboticssensor X X Artificial sensitive skin force sensors Pressure sensor X XDirect and indirect sensing of pressure and Distribution of pressure onsurfaces Security devices X X Intruder detection using vibration andimpact, for example, keypads for keyless locks or other interlockingsecurity devices Vibration sensors X X Direct and indirect detection ofvibrations with optional frequency selectivity Strain sensors X X Directand indirect detection of sudden strain with optional frequencyselectivity Detection of X X Failure analysis and impact localization ofimaging impacts sensor Accelerometer X X Miniaturized inertial andkinetic sensor devices for sensing acceleration and accelerationdirection Keyboard key X X Enhanced human touch sensitivity touch sensorHuman touch X X Enhanced human touch sensitivity force sensors/humantactile sensors Force sensing in X X Enhanced human touch sensitivitycapacitive touch in 3D capacitive touch sensor sensors applicationsSport and leisure X For example, a tennis court line to contact sensordetect the impact of ball on court boundary line Electrical X X Forcesensitive piezoelectric switches voltage is used to as a switch signalfor electrical circuitry Force sensitive X X Force sensitivepiezoelectric transistors voltage is used to open and close thetransistor gate Microgenerators X X Power generated and stored is forconversion proportional to time integrated of vibrational force energyto electrical energy

It is apparent from TABLE III that there are many different device usesfor the compositions and composite articles according to the presentinvention utilizing a dry PL and at least one dry ECL-P or dry DL-P.Many different types of sensors can be constructed using an inventivepiezoelectric capacitor, inventive kinetic piezoelectric device,inventive inertial piezoelectric device, and the composite articlesdescribed herein such as those illustrated in FIGS. 2-19. The differentuses include both direct force sensing applications as well as inertialforce applications using a dry PL and at least one dry ECL-P or dryDL-P. As has been previously discussed, sensors that are constructedusing direct force application to the dry PL have designs in which thedry PL is directly exposed to an applied force and the detectedpiezoelectric response is thought to be proportional to the timeintegral of the applied force. Similarly, sensors that are constructedusing inertial force that is generated in response to a direct forceemploy designs in which the direct applied force is converted to aninertial motion that produces a second applied force on the dry PL andthe piezoelectric response is thought to be proportional to the timeintegral of the second applied force produced by the inertial motion.

The last row of TABLE III above refers to a sensor type called amicrogenerator that is also called an energy harvesting device. Thereare many types of energy harvesting devices, utilizing the piezoelectriccapacitors, the kinetic piezoelectric devices, and the inertialpiezoelectric devices according to the present invention. Vibrationalenergy harvesting devices are energy harvesting devices wherein theapplied force to the energy harvesting device is primarily provided byvibrations, acoustic or otherwise, whose transmission of energy into thedevice results in the application of a measurable applied force to theenergy harvesting device, and thus an inertial or kinetic piezoelectricresponse results from such device. Four types of vibrational energyharvesting devices are known: electromagnetic,electrostative/capacitive, piezoelectric, and magnetostrictive.Vibrational energy harvesters utilizing a dry PL with a dry ECL-P or dryDL-P can be constructed using a variety of different designs. Anon-exhaustive listing of vibrational energy harvester designs utilizingpiezoelectric materials for converting vibrational energy intoelectrical energy suggests that piezoelectric material-based vibrationalenergy harvester device designs are of two basic types: 1) direct forceconversion designs (also known as kinematic energy harvesting designs)in which the piezoelectric material is directly exposed and directlycoupled to an applied force and the output signal from the piezoelectrictransducer is thought to be proportional to the time integral of theapplied force; and 2) inertial force conversion designs (also known asinertial energy harvesting designs) in which the applied force isindirectly coupled to the piezoelectric material so that the appliedforce is converted to an inertial motion that produces a second appliedforce on the piezoelectric material and the output signal from thepiezoelectric transducer is thought to be proportional to the timeintegral of the second applied force produced by the inertial motion.Energy harvesting devices of the direct force conversion design orkinematic energy harvesting design are also called direct force energyharvester, direct force energy harvesting devices, kinematic energyharvesters, or kinematic energy harvesting devices. Energy harvestingdevices of the inertial force conversion design are also called inertialenergy harvesters, inertial energy harvesting devices, inertialpiezoelectric energy harvesters, or inertial piezoelectric energyharvesting devices. Direct force conversion designs of kinematic energyharvesters utilize kinematic piezoelectric devices according to thepresent invention. Inertial energy harvesters utilize inertialpiezoelectric devices according to the present invention.

Those skilled in the art of vibrational energy harvester design wouldrecognize that direct force conversion designs are useful when large,high energy vibrational forces are available to excite the energyharvester while inertial force conversion designs and particularlyresonant inertial force conversion designs are useful when lower energyvibrational forces are available to excite the energy harvester.Examples of electromechanical schematics of direct force and inertialforce vibrational energy harvesters are illustrated in FIGS. 34 and 35.A resonant inertial force vibrational energy harvester comprised of acantilever beam is illustrated in FIG. 36.

More specifically, FIG. 34 shows a kinematic energy harvester schematiccomprised of an electromechanical schematic of kinetic piezoelectricdevice 195 illustrated in FIG. 31a that is in electrical communicationwith energy storing rectifying circuit 285 that is in electricalcommunication with electrical switches 290 that provide a means forliberating the stored electrical energy. In one embodiment, thekinematic energy harvester illustrated in FIG. 34 can be a strain sensoror strain gauge. In another embodiment, the rectifying circuit of FIG.34 need not include a means for storing electrical energy and kinematicpiezoelectric device 195 functions as a strain sensor or strain gauge.

FIG. 35 illustrates an inertial energy harvester schematic comprised ofan electromechanical schematic of inertial piezoelectric device 220shown in FIGS. 31b and 31c that is in electrical communication withenergy storing rectifying circuit 285 that is in electricalcommunication with electrical switches 290 that provide a means forliberating the stored electrical energy.

FIG. 36 illustrates an inertial energy harvester schematic comprised ofinertial piezoelectric device 220 illustrated in FIG. 31b shown as acantilever beam comprised of support 230, and composite article 135 withtip mass 225 that is in electrical communication with energy storingrectifying circuit 285 that is in electrical communication withelectrical switches 290 that provide a means for liberating the storedelectrical energy. Direct applied force 200 and inertial applied force210 are also shown with this device. In an alternate embodiment,inertial piezoelectric device 220 can be the piezoelectric plateresonator illustrated in FIG. 31 c.

It is intended that the representations of the kinematic and inertialenergy harvesters are non-limiting with respect to the incorporation ofa kinetic piezoelectric device, an inertial piezoelectric device, orpiezoelectric capacitor, all according to the present invention.

For example, a vibrational energy harvester can be comprised of apiezoelectric capacitor with a dry PL and at least one dry ECL-P inelectrical communication with an energy storing rectifying electricalcircuit comprised of a diode bridge and a capacitor wherein thecapacitor is in electrical communication with a means to liberate theenergy stored in the capacitor. The piezoelectric capacitor can beimpedance matched to the rectifying circuit, or not.

A vibrational energy harvester can be of a kinematic energy harvestingdesign and comprise a kinetic piezoelectric device further comprising apiezoelectric capacitor with a dry PL and at least one dry ECL-P inelectrical communication with an energy storing rectifying electricalcircuit further comprised of a capacitor and a means to liberate theenergy stored in the capacitor. In other embodiments, the vibrationalenergy harvester can be of the inertial energy harvesting design asdescribed above.

The design and use of capacitive touch sensors for tactile userinterfaces in the design of electrical devices is well known and hasbeen implemented in mobiles phones and computer displays. Those skilledin the art of capacitive touch sensors recognize that there are at leasttwo types of capacitive touch sensors: (1) surface capacitance touchsensors and (2) projection capacitance touch sensors.

A surface capacitive touch sensor is comprised of a dielectricinsulating layer with a conductive coating on the backside held at afixed voltage and at least 4 electrical contact probes on the opposingfront side. Physical contact of a conductor at virtual ground with thefront side leads to changes in capacitance of the structure that can beread using the contact probes on the front side. The differences incapacitance measured at each of the 4 probes is then used to determinethe location of the contact. Surface capacitance touch sensors requirethat the material contacting the sensor surface beelectrically-conductive.

The simplest form of a projection capacitive touch sensor is comprisedof a dielectric insulating layer with at least one X-Y addressableelectrode array. The array can be on the same side of the dielectriclayer or on opposing sides of the dielectric layer. The array is used toprobe the capacitance either across the thickness of the dielectriclayer or along the surface of the dielectric layer, depending on thetype of X-Y addressable electrode array that is used. The X-Yaddressable electrode array that is used to probe capacitance is scannedusing a predetermined pattern that corresponds to specific positions onthe surface area of the array. A change in the measured capacitance atspecific positions correlates with touch screen contact at the sameposition and this acquired position sensitive touch information is usedby the device to initiate certain actions like registering a keystrokeon a keypad. In most common usage, the capacitive touch sensors used inelectronic devices are employed to detect the presence or absence of aphysical contact at a certain position on the touch sensor screen.

More recently, capacitive touch sensors have been designed to have anadditional capability of determining how much force is associated with acontact at a certain position on the touch sensor. Capacitive touchsensors that include this capability are known as force-sensitivecapacitive touch sensors. The information provided by a force-sensitivecapacitive touch sensor includes the position where the contact to thesensor was initiated as well as the force that was applied during thecontact with the touch sensor surface. The latter information is alsoused to initiate certain actions and responses by the device that arespecifically associated with the degree of contact force associated withthe physical contact to the touch sensor surface. Such actions caninclude tactile or auditory feedback as well as display of newinformation that allows the user to further direct the actions of thedevice. Although force-sensitive capacitive touch sensors can be opaqueto visible light or even colored, it is often desirable thatforce-sensitive capacitive touch sensor be transparent so that they canbe located over a light emitting display element that indicates wherethe positions of appropriate contact and force application are locatedon the touch screen surface. A compact, human-readable tactileelectronic interface is thereby formed by combining a transparent forcesensitive capacitive touch sensor with a light emitting display.

Composite articles according to the present invention can be designed asa useful means of contact force sensing in inventive force-sensitivecapacitive touch sensors.

FIG. 37 illustrates force-sensitive touch display 300 comprisingcapacitive touch sensor 305 that is designed to sense a grounded objectand to determine the position of the grounded object in the plane of thesensor and to represent the position as a set of x and y coordinates ona Cartesian plane, further comprised of force sensing backplane 310comprised of dry PL 30 contiguous with dry ECL-P 25 containing (b)particles and dry ECL-P 50 also containing (b) particles. Force sensingbackplane 310 that is a piezoelectric capacitor, senses the zdirectional force exerted on capacitive touch sensor 305 x-y plane.Capacitive touch sensor 305 is in electrical communication (dottedlines) with signal processing electronics 315 and in mechanicalcommunication with force sensing backplane 310 (that can also be calleda “force-sensitive touch device”) that is a composite article accordingto the present invention. In one embodiment, signal processingelectronics 315 can comprise a rectifying circuit and a sample and holdcircuit with a voltage output. In another embodiment, signal processingelectronics 315 can comprise a means for storing electrical energy and ameans for discharging electrical energy. For example, force sensingbackplane 310 can be a kinetic piezoelectric device, an inertialpiezoelectric device, or a piezoelectric capacitor.

In one embodiment of force-sensitive touch display 300, force sensingbackplane 310 and capacitive touch sensor 305 are optically transparentor sufficiently transparent, that is, they are optically low lightscattering and low light absorbing. By “optically transparent,” we meanthat the % optical transmissions for both the force-sensitive touchdisplay and the capacitive touch sensor are independently greater than50%, or even at least 80%, based on total impinging actinic radiation.

Another useful method for acquiring the position of physical contact ona touch screen surface is the use of a resistive contact touch sensor(also known as a resistive touch sensor). A simple 4-wire configurationfor a resistive contact touch sensor can be comprised of twoelectrically-conducting surfaces that face each other and are separatedby a gap. Each electrically-conducting surface has a pair of parallelelectrical contacts at opposite edges of the surface making a total of 4electrical contacts that require 4 wires. The opposingelectrically-conducting surfaces can have their electrode pairspositioned perpendicular to each other. There is a first set ofelectrodes on the first electrically-conducting surface and a second setof electrodes on the second electrically-conducting surface that opposesand faces the first surface positioned perpendicular to the first set ofelectrodes. During use, signal processing electronics are used to applya voltage to a set of electrodes on one of the electrically-conductingsurfaces. During a contact event, the opposing electrically-conductingsurfaces come into physical contact with each other when physicallypressed together thereby bringing the two opposingelectrically-conducting surfaces into electrical communication. Thevoltage at the contact point relative to ground is measured by thesecond set of electrodes and is used to calculate the contact positionon the first electrically-conducting surface. The signal processingelectronics then repeat the measurement by applying the voltage to thesecond set of electrodes while using the first set of electrodes on thefirst electrically-conductive surface to measure the voltage relative toground at the contact point. The signal processing electronics use themeasured voltages from the two electrically-conducting surfaces andinternal calibration information to determine the x-y location of thecontact position that resulted in electrical communication between thetwo electrically-conductive surfaces. This acquired position informationof the physical contact location is fed by the signal processingelectronics to a device used to initiate certain actions likeregistering a keystroke on a keypad. In most common usage, the resistivetouch sensors used in electronic devices are employed to detect thepresence or absence of a physical contact at a certain position on thesensor.

More recently, resistive touch sensors have been designed to have theadditional capability of determining how much force is associated with acontact at as certain position on the sensor. Resistive touch sensorsthat include this capability are known as force-sensitive resistivetouch sensors. The information provided by a force-sensitive resistivetouch sensor includes the position where the contact to the touch sensorwas initiated as well as the force that was applied during the contactto the touch sensor surface. The latter information is also used toinitiate certain actions and responses that are specifically associatedwith the degree of contact force associated with the physical contactwith the touch sensor surface. Such actions can include tactile orauditory feedback as well as display of new information on the devicetouch screen that allows the user to further direct the actions of thedevice. Although force-sensitive resistive touch sensors can be opaqueto visible light or even colored, it is often desirable thatforce-sensitive resistive touch sensor be transparent so that they canbe located over a light emitting display element that indicates wherethe positions of appropriate contact and force application are locatedon the touch screen surface. A compact, human-readable tactileelectronic interface is thereby formed by combining a transparentforce-sensitive resistive touch sensor with a light emitting display.

Composite articles according to the present invention can be designedfor use as a means of contact force sensing in inventive force-sensitiveresistive touch sensors.

FIG. 38 illustrates force-sensitive touch display 325 comprisingresistive touch sensor 320 according to the present invention that isdesigned to sense an object that is touching the sensor surface and todetermine the position of the object in the plane of the sensor andrepresent the position as a set of x and y coordinates on a Cartesianplane, comprising force sensing backplane 310 (that can also be called a“force-sensitive touch device”) that is a composite article according tothe present invention comprised of dry PL 30 contiguous with both dryECL-P 25 and dry ECL-P 50. Force sensing backplane 310 that is apiezoelectric capacitor, senses the z directional force exerted on theresistive touch sensor x-y plane. Resistive touch sensor 320 is inelectrical communication (dotted lines) with signal processingelectronics 315 and in mechanical communication with force sensingbackplane 310. In one embodiment, signal processing electronics 315 caninclude a rectifying circuit and a sample and hold circuit with avoltage output. In another embodiment, signal processing electronics 315can comprise a means for storing electrical energy and a means fordischarging electrical energy. For example, force sensing backplane 310can be a kinetic piezoelectric device, an inertial piezoelectric device,or a piezoelectric capacitor.

In one embodiment of force-sensitive touch display 325 force sensingbackplane 310 and resistive touch sensor 320 are optically transparentor sufficiently transparent, that is they are optically low scatteringand low light absorbing. By “optically transparent,” we mean that the %optical transmissions for both the force-sensitive touch display and theresistive touch sensor are independently greater than 50%, or even atleast 80%, based on total impinging actinic radiation.

Methods of Making Composite Articles and Devices

The composite articles according to the present invention can beprepared using the following conditions and equipment. For example,representative composite articles illustrated in FIGS. 2 through 19 canbe fabricated using a variety of methods.

Those skilled in the art of piezoelectric materials would recognize thata dry PL can be comprised of one or more materials that have thecharacteristic of generating charge when a force is applied thereto.Such materials include but are not limited to inorganic and organiccrystalline materials, inorganic and organic polycrystalline materials,inorganic and organic vitreous materials, inorganic and organic glassceramic materials, as well as inorganic and organic polymers, glasses,and composites. Inorganic piezoelectric materials are prepared in avariety of formats including layers, films, templated films, singlecrystals, and complex three-dimensional shapes that are molded ormachined. In the case of films, polycrystalline slabs, single crystal,and sintered shapes, a quantity of inorganic piezoelectric material isoften prepared as a feedstock using a multistep process that will now bedescribed.

This representative description is not meant to be exclusive and it isrecognized that other methods of preparation are possible. Thosefamiliar with the art of preparation of inorganic materials recognizethat an initial step of preparation of a dry PL would be mixing one ormore appropriate starting materials using various mixing methods thatinclude coprecipitation, grinding, ball milling, dispersion milling,spray drying, or any powder mixing method known in the art of powdermixing. The starting materials can then be heated in an appropriatecontainer to a predetermined temperature, often in a controlledatmosphere using any heating technique familiar to those skilled in theart of material preparation. The starting materials can be heated sothat solid state diffusion occurs between any mixture of startingmaterials so that the desired inorganic compound with desired crystalstructure is formed. Those skilled in the art of inorganic materialpreparation by solid state diffusion reactions appreciate thatoften-mixed starting materials must be remixed after each heating bygrinding, ball milling, hammer milling or other mixing methods, and thenreheated repeatedly until the desired inorganic compound with thedesired crystal structure that is formed is present in sufficient purityto enable the use of the material for piezoelectric applications. Thepiezoelectric material purity is often assessed by multiple analyticaltechniques familiar to those skilled in the art of inorganic materialpreparation including, but not limited to, x-ray diffraction, infraredspectroscopy, density measurements, scanning and transmission electronspectroscopy, metallographic optical examination using microscopy, andelemental analysis. The polycrystalline single-phase inorganic materialis then used to form polycrystalline or single crystalline forms andshapes by further high temperature processing. Single crystal inorganicmaterials are formed using any suitable crystal growth method known inthe art of crystal growth including, but not limited to, methods such asthe Czochralski method for crystal growth; crystal growth from vaporphase using such methods as chemical vapor transport; epitaxial methodsfor crystal growth to form single crystal layers; flux based methods forcrystal growth, heat exchange methods for crystal growth, lasercrystallization methods for crystal growth, and other methods known tothose skilled in the art of crystal growth.

After a suitable phase of the piezoelectric material is formed as a bulksingle crystal it can be cut and polished for the desired application.Alternatively, a polycrystalline inorganic material comprised of thedesired crystalline phase can be further processed into polycrystallineshapes using any method known to those skilled in the art of formingceramic shapes including, but not limited to, tape casting followed bythermal consolidation, slip casting followed by thermal consolidation,isostatic and non-isostatic pressing followed by thermal consolidation,and hot pressing. Those skilled in the art of ceramic materialprocessing know that subsequent machining or finishing operations areoften carried out on the thermally consolidated ceramic shape including,but not limited to, such finishing operations as dicing, machining, andpolishing the ceramic, glass-ceramic, or vitreoceramic shape to thedesired final dimensions. Those skilled in the art of ceramic materialprocessing know that subsequent annealing can be used to remove orreduce stress induced by finishing operations performed on the ceramicpart. Inorganic piezoelectric material films, both polycrystalline andsingle crystal, are alternatively prepared using any method familiar tothose skilled in the art of thin film preparation, including, but notlimited to, physical vapor deposition methods like vacuum evaporation,sputtering methods of all types, chemical vapor deposition, molecularbeam epitaxy, atomic layer deposition, plasma enhanced vapor depositionmethods of all types, and sol-gel coating by any method known in the artof sol-gel coating followed by thermal consolidation. Single crystalfilms of piezoelectric inorganic material are polished if necessary.

Polymeric piezoelectric materials can be prepared by polymerization ofsuitable monomer molecules of the same or different chemical compositionto form a two or three-dimensional network of chemically bonded randomlyor block recurring monomer units. Any suitable polymerization methodsknown to those skilled in the art of polymer preparation can be used toform piezoelectric polymers provided that the method includes a means ofproviding 1) initiation of chain growth from the desired monomer(s); 2)propagation of chain growth utilizing the desired monomer(s); and 3)termination of chain growth. A non-exhaustive listing of suchpolymerization methods includes photopolymerization, thermalpolymerization, radical induced polymerization, reversibleaddition-fragmentation chain transfer, ring opening polymerization, andplasma polymerization. The desired piezoelectric polymer can be isolatedas a solid from a polymerization reaction solution or dispersion by anymethod known in the art of polymer preparation. Representative means forpost-processing polymers include, but are not limited to: 1)redispersion of the polymer into a suitable solvent followed by coatingonto a substrate using any method known in the art, and drying to removethe residual solvent using any method known in the art of drying; and 2)thermally processing the polymer by any polymer processing method knownto those skilled in the art of polymer processing to form a web ofpolymer of a desired length and thickness. Coating methods including,but are not limited to, vapor deposition of all types, slot coating, rodcoating, curtain coating, spin coating, dip coating, spray coating,electrospray coating, brush coating, and roller coating.

Coating methods for forming a web of a desired thickness include, butare not limited to, extruding a heated polymer mass through a slot diefollowed by optionally drawing and tentering the extruded polymer web todesired length and thickness. When a polymer web is stretched in twodifferent directions during fabrication as, for example, when anextruded polymer ribbon is both drawn and tentered, it is said to bebiaxially oriented. Alternatively, a polymer web can be formed bycoating a suitable solution of polymer onto a moving surface followed bydrying and stripping the film off the surface to form a free-standingpolymer ribbon. The moving surface can be a rotating drum.Alternatively, the moving surface is a flexible web that can becontinuous.

Those skilled in the art of polymeric piezoelectric materials know thatsuch materials often can have several crystalline phases with onecrystalline phase being preferred for piezoelectric response. Forexample, it is well known that the beta phase of polyvinylidene fluoride(β-PVDF) is the best phase of this crystalline polymer for piezoelectricresponse. Those skilled in the art of polymer processing know thatvarious operations can be carried out to promote the formation of adesired crystalline phase in a polymeric piezoelectric material. Anon-exhaustive list of such operations includes drawing and tentering,thermal annealing, application of electric field and heat, and solventtreatment. The presence of the desired crystalline phase in the polymercan be verified by any suitable means known in the art of polymercharacterization including, but not exclusively limited to, x-raydiffraction, infrared spectroscopy, raman spectroscopy, differentialthermal analysis and other forms of calorimetry including differentialscanning calorimetry, dynamic mechanical analysis, rheological analysis,and microscopies of all types including scanning tunneling microscopyand kelvin probe microscopy.

Those skilled in the art of piezoelectric materials would know that onlymaterials that crystallize with structures described by a certain subsetof all crystalline classes show piezoelectric behavior. Only 20 pointgroups out of the 32 possible points that are used to describe crystalstructures allow piezoelectric behavior. Piezoelectric behavior is notobserved in materials whose crystal structure has a center of symmetry.Those skilled in the art would also recognize that the piezoelectricbehavior of a piezoelectric material possessing a permanent dipolemoment within the crystal structure—that is, a ferroelectricpiezoelectric material—can be improved by the application of polingtechniques. Initially, the dipoles in a piezoelectric material havingpermanent dipoles in the structure are randomly oriented within volumeof the structure and no net macroscopic dipole moment is measurable. Thepoling of a piezoelectric material refers to the process by which therandom three-dimensional orientation of the permanent dipoles present ina piezoelectric material that has a permanent dipole in each domain ofthe crystal structure can be aligned in order for the piezoelectriclayer to show macroscopic polarization due to dipole alignment. Thealignment of the dipoles to produce macroscopic polarization in thepiezoelectric material layer enhances the piezoelectric response of thematerial. In particular, the force induced charge generated by thepiezoelectric layer having permanent dipoles in the structure can beenhanced when the permanent dipoles are aligned by the poling process.The poling process is accomplished by the application of an electricfield across the piezoelectric material. The material can be in the formof a layer or a preformed three-dimensional shape. The electric fieldcan be applied by positioning the piezoelectric material so that aportion of the piezoelectric material is proximate to one electrode anda portion of the piezoelectric material is proximate to anotherelectrode where one electrode is at high potential and the otherelectrode is at a different potential. The two electrodes are in anydesired spatial relationship with the provision that they aresufficiently proximate to each other to generate the desired electricfield when an external voltage is applied. Those skilled in the art ofpiezoelectric materials know that a common configuration for poling apiezoelectric layer has a piezoelectric layer with one surfacecontiguous to an electrode and the opposing surface of the piezoelectriclayer contiguous to a second electrode. Poling occurs when a voltagesufficient to produce dipole alignment in the piezoelectric layer isapplied between the two electrodes, with the optional application ofheat to improve dipole mobility. It is understood by those skilled inthe art that the voltage is controlled to minimize the possibility ofdielectric breakdown of the piezoelectric layer or article itself. Thoseskilled in the art of poling also understand that there are othermethods of poling piezoelectric materials. A frequently used method ofpoling piezoelectric polymers is corona charging where a plasmadischarge in a gas is used to deposit positively or negatively chargedspecies on the surface of the piezoelectric layer to induce dipolemobility within the piezoelectric layer and hence pole the layer. In oneembodiment, the dry electrically-conductive layers ECL and ECL-P areused to pole the piezoelectric layer during the fabrication of theinventive composite article. In another embodiment, the piezoelectriclayer is poled before application of any electrically-conductive layerin the inventive article. Corona poling may be used at any appropriatetime as a poling procedure during the fabrication of the inventivecomposite article to promote poling of the piezoelectric layer in theinventive composite article.

A substrate such as substrate 140 shown in composite article 135illustrated in FIG. 15 can be comprised of materials that are suitablefor its intended use. For example, a substrate can be an electricalinsulator and a dielectric in nature. Alternatively, a substrate can beelectrically conductive and can be comprised essentially of one or moreelectrically-conductive metals or other electrically-conductivematerials. Still again, a substrate can be comprised of a semiconductormaterial. A substrate material can also be thermally conductive orthermally insulating.

Moreover, a substrate can be a multilayer structure comprised of anelectrically conductive layer with a contiguous dielectric layer, suchas an electrically-conductive metallic layer with a contiguousdielectric layer. Alternatively, a substrate can be a multilayerstructure comprised of: a semiconductor layer with a contiguousdielectric layer; a thermally conductive layer with a contiguousdielectric layer; a first thermally conductive layer with a secondcontiguous thermally conductive layer; or a first electricallyinsulating layer, a second contiguous dielectric layer disposed andoverlaying thereupon, and a third dielectric layer contiguous with thesecond dielectric layer wherein the dielectric layers have the same ordifferent thermal conductivity.

In still other embodiments of composite articles, a substrate can be amultilayer structure comprised of a first electrically insulating layer,a second contiguous dielectric layer disposed and overlaying thereupon,and a third dielectric layer contiguous with the second dielectric layerwherein the layers in the structure can have the same or differentthermal conductivity.

In yet other embodiments, a substrate can be a multilayer structurecomprised of an electrically conductive layer, a first contiguousdielectric layer disposed and overlaying thereupon, and a seconddielectric layer contiguous with the first dielectric layer.

Another arrangement of layers in a substrate can be comprised of a dryelectrically conductive layer, a first contiguous dry dielectric layerdisposed and overlaying thereupon, and a second dry dielectric layercontiguous with the first dry dielectric layer wherein the first andsecond layers are thermally conductive. The substrate can also be asemiconductor with a contiguous dielectric layer.

For example, a substrate material can be comprised of any suitableelectrically-insulating, dielectric materials including, but not limitedto, non-electrically-conducting polymers and filled polymers wherein thepolymer fill is non-conducting; engineering plastics such as nylons;liquid crystalline polymers; polyetherketone polymers and copolymersderived in part at least from an etherketone; polyimide polymers andtheir copolymers; imagewise patternable positive and negativephotoresists such as polyimide photoresists and SU-8; inorganic polymerssuch as insulating silicones containing siloxane networks of all types;insulating oxides of all types such as aluminum oxide, silicon oxide andsilicon oxide based glasses, titanium oxide, phosphate glasses, borateglasses, aluminosilicates, vitreoceramics including those containingalkali and alkaline earth metals cations, glassy ceramics includingthose containing alkali and alkaline earth metals cation, zirconiumoxide, hafnium oxide, binary and ternary nitrides like aluminum nitride,gallium nitride; and any material with a resistivity greater than 10⁷ohm-cm and a band gap greater than 1 eV. Electrically-insulating andthermally-conductive dielectric materials useful as substrate materialsinclude, but are not limited to, diamond, boron nitride, aluminumnitride, and composites thereof. Useful semi-conducting materials forsubstrates include, but are not limited to, p-type and n-type silicon,p-type and n-type silicon carbide, p-type and n-type germanium, II-VIsemiconductors such as GaAs and InP, III-V semiconductors such as CdSand CdTe, and thermoelectric materials such as Bi₂Te₃. Usefulelectrically-conductive materials for the fabrication of a substrateinclude, but are not limited to, metals, metal alloys, compositescontaining metals, and other types of electrically-conductive particlessuch as carbon, conductive forms of carbon including graphemes andcarbon nanotubes of all types, and conductive polymers such aspolyaniline based polymers.

A substrate used in a composite article according to the presentinvention can be optically transparent or optically non-transparent. Forexample, it can have an optical absorption in a specific region of theelectromagnetic spectrum, an optical absorption in at least onewavelength, or optical absorption within two or more wavelength regions.In addition, a substrate can have an embedded thermoelectric elementtherein.

A substrate for any composite article according to this invention can befabricated using any method familiar to those skilled in the artincluding machining, extruding, roll forming, hydroforming, bending,curling, decambering, deep drawing, expanding, hemming and seaming,sheet forming, ironing, laser cutting, photochemical machining,perforating, press brake forming, punching, roll forming, rolling,spinning, stamping, water jet cutting, and drawing and tentering to forma material with desired shape and dimensions. Although substrate 140shown in FIG. 15 is shown as a planar layer, a substrate can have anyshape, and it can be formed of multiple layers each of which can befabricated by any method known in the art for fabricating contiguouslayers. Thus, useful methods for fabricating contiguous layers include,but are not limited to, co-extrusion methods, cladding methods,lamination methods, injection molding methods, and deposition methodssuch as solvent casting, spin coating, dip coating, spray coating, brushcoating, extrusion, slot coating, curtain coating, electrospraying,physical vapor deposition, in-situ chemical polymerization,photopolymerization, thermal polymerization, electrodeposition,precision liquid dispensing, layer formation utilizing heat or radiationcuring methods, gravure and flexographic methods for forming continuousfilms, screen printing, drop-on-demand inkjet printing, and continuousinkjet printing.

Conformal surfaces are surfaces in which the angle between the twosurfaces is invariant at every point. A characteristic of conformallayers is uniform thickness of one disposed layer on a second surface atevery point on the second surface. In general, the layers of a compositearticle according to the present invention can be conformal. In otherembodiments, the layers of a composite article according to the presentinvention are non-conformal. In still other embodiments, some layers ofthe composite article can be conformal while other layers arenon-conformal.

As an illustration of how composite articles of the present inventioncan be prepared, the preparation of composite article 135 shown in FIG.15 is used as an example, but is not considered exclusive of other waysto prepare such elements. Composite article 135 can be fabricated bydisposing each illustrated layer in a suitable fashion so thatcontiguous layers are arranged properly. For example, the followingsteps can be carried out: dry ECL-P 50 can be disposed upon substrate140; dry PL 30 can be disposed and arranged contiguously with anopposing surface of dry ECL-P 50; dry ECL-P 25 can be disposed andarranged contiguously with an opposing surface of dry PL 30. Anoutermost dry protective layer (not shown) can be optionally disposedand arranged contiguously with an opposing surface of dry ECL-P 25. Thedisposition and arrangement of the various layers can be accomplishedusing any method known to those skilled in the art of fabrication,disposition, and arrangement of material layers like dry ECL-P 25, dryECL-P 50, dry PL 30, and the outermost dry protective layer (not shown).It is recognized that if dry PL 30 is heat sensitive, some fabricationmethods may require that it be poled after fabrication to ensurepiezoelectric response. While adhesive layers are not shown in FIG. 15,they can be present between opposing surfaces of any contiguous layers.

It is recognized that the order of the fabrication steps for assemblingan inventive composite can be changed from that just described. Forexample, any combination of dry ECL-P's, dry ECL's, and dry PL's can bepre-fabricated to ensure that the desired layers are contiguous andpre-fabrication and pre-assembly steps can be followed by dispositionand arrangement of the preassembled dry PL with dry ECL-P's and dryECL's onto one surface of a support. In addition, an outermost dryprotective layer can be applied to a dry ECL-P in a preassembledfashion, or it can be applied after a dry PL and dry ECL-P's and dryECL's have been disposed onto a substrate. The order of variouscontiguous layers within a composite article according to the presentinvention can be determined by its desired utility.

Besides dry ECL's and ECL-P's containing the (a) electrically-conductivematerials described above, a dry ECL or dry ECL-P according to thisinvention can also be formed from a metallic film that can be depositedby electrochemical deposition, electro-less deposition, electrospraying,or deposition from the vapor phase by means of such methods as chemicalvapor deposition, plasma deposition, plasma enhanced vapor deposition orphysical vapor deposition or sputtering, or atomic layer depositionoptionally plasma-enhanced to mention a few. Other types ofelectrically-conductive layers can also be formed by slot coating,curtain coating, airbrush, screen printing, gravure, flexographic,solvent casting, spin coating, dip coating, spray coating, brushcoating, extrusion, lamination, in-situ chemical polymerization,photopolymerization, thermal polymerization, molding including injectionmolding, precision liquid dispensing including heat and radiation curingmethods, drop-on-demand inkjet printing, or continuous inkjet printing.

Dry ECL-P:

Dry ECL-P's can be prepared by similar methods to dry ECUs, with thedifference being the addition of (b) particles to theelectrically-conductive materials. The presence of (b) particles to theEC-P composition may or may not change the composition compatibilitywith a given deposition process. The conductive component of the dryECL-P comprises any suitable material or composition that meets theresistivity requirement as described above and includes but is notlimited to, silver, gold, nickel, platinum, palladium, copper, nickel,iron, titanium, silver coated copper, silver coated nickel, indium,gallium and its alloys, and aluminum; in addition to various types ofcarbon including graphite and graphene; organic and inorganic conductingpolymers; and polyelectrolytes. Further examples of such materials aredescribed above.

FIGS. 2 through 21 describe inventive composite articles wherein the (b)particles are shown to be randomly and uniformly dispersed in the dryECL-P. However, it is recognized this is not a necessary requirementaccording to the present invention. The (h) particles can be distributedin a non-random or non-uniform manner in both two and three dimensionsin the dry ECL-P. For example, (b) particles can be segregated at thetop region of the thickness of the dry ECL-P with fewer particles beingpresent in the remainder of the thickness. Alternatively, (b) particlescan be segregated in the middle region of the thickness of the dry ECL-Pwith fewer particles being present in the remainder of the thickness.Still again, (b) particles can be segregated in the bottom region of thedry ECL-P with fewer particles being present in the remainder of thethickness. It is also possible that the (b) particles can be distributedin a gradient throughout the thickness of the dry ECL-P.

The dry ECL-P of the inventive composite articles illustrated in FIGS.2-21 are readily fabricated by coating a wet EC-P composition comprisedof a (d) solvent medium (if needed), (b) particles, (c) a bindermaterial, and (a) an electrically-conductive material, all as describedabove so that the resulting dry ECL-P is arranged contiguously with thedesired layer or substrate. Suitable coating methods have previouslybeen disclosed above for providing a dry ECL.

In some embodiments, the (b) particles can be arranged at predeterminedpositions in both two and three dimensions within the dry ECL-P. Thiscan provide an advantage of tailoring the non-uniformity of the appliedstress on the dry PL for any given application to optimize thepiezoelectric response from the composite article. Arranging the (b)particles at a predetermined position is also called “ordering” the (b)particles. It is possible to order the (b) particles so that they occupypredetermined positions by printing or depositing the (b) particlesusing known methods including, but not limited to, flexographicprinting, gravure printing, screen printing, lithographic patterningtechniques, lamination and etching techniques, seed-layer growthtechniques where the particles are deposited in a patterned, regular, oraligned configuration or manner, at a desired location within thethickness of the dry ECL-P. This can be realized by multiple-stepprocessing, whereby multiple layers of an EC-P composition or ECcomposition are deposited at the same or different thicknesses so thatthe (b) particles are residing at a desired location or position withinthe resulting composite dry ECL-P layer.

The (b) particles can be two-dimensional or three-dimensional. (b)Particles that have a flake-like shape are considered to have a“two-dimensional” structure even though there is a finite thickness ofsuch (b) particles. (b) Particles that have a rod-like shape are calledacicular (b) particles and these have a high aspect ratio (ratio oflength to width) which is greater than 1.5 and can be 100 or more.Oriented (b) particles are those whose spatial position relative to oneanother is defined as being not statistically random. Methods fororienting (b) particles include, but are not limited to, the use ofmagnetic fields, electrical fields, or shear force often associated withsolution coating methods so that the (b) particles are selectivelyoriented during the formation of the dry ECL-P.

Methods used to provide either two-dimensional or three-dimensionaloriented (b) particles in composite articles according to the presentinvention include various printing and deposition techniques. Additionaluseful fabrication methods for providing oriented (b) particles in a dryECL-P or dry DL-P include fabrication of oriented (b) particles that areanisotropically etched after deposition to create a non-spherical shapeand a desired directional orientation.

Some composite articles according to the present invention can beprepared with multiple dry ECL's, dry ECL-P's, or both dry ECL's and dryECL-P's. Such embodiments can be achieved by using multiple stepprocesses for forming the layers, each layer being provided by the sameor different methods, and each layer comprising the same or differentcompositions. For example, a dry ECL or dry ECL-P can be formed using avacuum deposition technique, solution casting technique, a printingmethod including 3D printing, electrospraying method, lithographicpatterning method, screen printing method, or any other method known inthe art of deposition. A second dry ECL-P or dry ECL layer arrangedcontiguously with the first dry ECL or dry ECL-P can then be providedusing the same or different method or technique. A third dry ECL or dryECL-P can be provided similarly with the same or different method ortechnique. The EC or EC-P compositions used in the three layers can bethe same or different, depending upon whether (b) particles are present.

It is known to those skilled in the art of electrical circuits that thereduction of contact resistance for metallic films is desirable and thisis often achieved by creating layered electrically-conductive films withdesired electrical properties. The (b) particles in each layeredelectrically-conductive layer can be the same or different. In addition,the type of (b) particles in various dry ECL-P's can be the same ordifferent, depending upon individual dry ECL-P materials, design, andpurpose. It is understood that the individual layers in a multilayercomposite article according to this invention can interact with eachother and that such interlayer interactions can be detrimental andunpredictable. As a result, the characteristics and behavior of anentire multi-layer structure of a composite article should be consideredas a whole for any intended application.

The spatial position of a dry ECL or dry ECL-P can be varied in adesired construction of a composite article. For example, in embodimentshaving two electrically-conductive layers, one can be a dry ECL and theother a dry ECL-P, and they can be positioned on opposing surfaces of adry PL. In other embodiments, a dry ECL and a dry ECL-P can bepositioned on the same opposing surface of a dry PL, and such dry ECLand dry ECL-P can be in direct or non-direct electrical communicationwith each other.

Non-Electrically-Connected Co-Planar Patterned Electrodes

The electrodes described above (both dry ECL's or dry ECL-P's) aredefined as essentially uniform dry layers in the composite articles.

However, it is also possible according to the present invention for oneor more pairs of non-electrically-connected (or non-electricallycommunicating) co-planar patterned electrodes to be present in acomposite article. Each of these pairs can be arranged as regular orirregular patterns in the same plane disposed contiguously with asurface of another layer such as a dry PL or dry DL-P, or on a substrate(such as an insulative substrate material). Each co-planar patternedelectrode in each pair is arranged on or shares a single surface of acontiguous dry layer or support material. There can be two or more pairsof such non-electrically-connected co-planar patterned electrodes, allsharing the same single surface.

If the composite article contains an ECL-P or a DL-P, it is notnecessary that any of the pairs of non-electrically-connected co-planarpatterned electrodes contain (b) particles. However, if there is noECL-P or DL-P in the composite article, at least one pair ofnon-electrically-connected co-planar patterned electrodes must Contain(b) particles.

Such non-electrically-connected co-planar patterned electrodes can beprepared from an EC-P or EC composition as described above. By design,each of the pair of non-electrically-connected co-planar patternedelectrodes are in the same plane, but they are not electricallyconnected or in communication with each other, and can be separated fromeach other by gaps filled with air or with non-electrically-conductivematerials (such as a dielectric or insulative materials). Each pair ofsuch non-electrically-connected co-planar electrodes can be arrangedwithin the same plane in predetermined regular or irregular patterns,for example as predetermined concentric circles (see for example, FIG.45), interdigitated “fingers” (see for example, FIGS. 41 and 42),serpentine designs (see for example, FIG. 46), or they can be formed ina regular or irregular pattern of wires forming a mesh or grid, or bedisposed as any desired shapes, convex or concave non-intersectingpolygons, non-intersecting chaotic patterns, or any other pattern that askilled worker could design.

Thus, in such embodiments according to the present invention, acomposite article can comprise at least one pair (at least two)non-electrically-connected co-planar patterned electrodes that are inthe same plane on a surface, but which are not directly electricallyconnected to (or in electrical communication with) each other. In someembodiments, one or both of a pair of non-electrically-connectedco-planar patterned electrodes can be composed of an EC composition orEC-P composition according to this invention, which EC composition orEC-P composition can be arranged adjacent to an opposing surface of adry PL, insulative substrate, or dry DL-P using any suitable depositiontechnique or process that would be readily apparent to one skilled inthe art. For example, such non-electrically-connected co-planarpatterned electrodes can be provided from an EC composition or EC-Pcomposition using gravure printing, screen printing, inkjet printing,stenciling, airbrushing, or any other printing or deposition processthat would be readily apparent to one skilled in the art.

In some embodiments, each non-electrically-connected co-planar electrodeof a pair independently can have physical dimensions of at least 100Angstroms and up to and including 5 mm dry width, and the dry thicknesscan be the same or different. Each electrode length can be any desireddimension suitable for a particular use and pattern design.

In some embodiments according to this invention, one or more pairs ofnon-electrically-connected co-planar patterned electrodes can be formedusing an EC composition, and used in combination with a dry DL-P asdescribed herein. Thus, each of these pairs can be disposed on the sameor opposing sides of the dry DL-P.

In some embodiments, the composite articles described above can furthercomprise an insulating substrate (as described above) as well as one ormore pairs of co-planar patterned electrodes, all of which are arrangedcontiguously between the insulating substrate and a dry PL.

In such embodiments, it is also possible for the composite article tocomprise a first dry electrically-conductive layer containing no (b)particles (first ECL), which first ECL is arranged contiguously with thesecond opposing surface of the dry PL. Further, the composite articlecan comprise a first dry electrically-conductive layer containing (b)particles (first ECL-P) that is arranged contiguously with the first dryECL that is arranged contiguously with the second opposing surface ofthe dry PL.

In other embodiments, a composite article according to the presentinvention can comprise a pair of co-planar patterned electrodes that arearranged contiguously with the first opposing surface of a dry PL, andat least one dry DL-P that is arranged contiguously over the pair ofco-planar patterned electrodes.

In such embodiments, the composite article can further comprise a firstdry electrically-conductive layer containing no (b) particles (firstECL), which first dry ECL is arranged contiguously with the secondopposing surface of the dry PL. Moreover, a dry electrically-conductivelayer containing (b) particles (dry ECL-P) can be arranged contiguouslywith the first dry ECL that is arranged contiguously with the secondopposing surface of the dry PL.

FIGS. 39-42 illustrate some representative embodiments illustratinginterdigitated non-electrically-connected co-planar patterned electrodesaccording to the present invention, but it is to be understood thatthese embodiments are not limiting to what composite articles may bepossible within the present invention.

FIG. 39 shows composite article 330 wherein twonon-electrically-connected (and interdigitated) co-planar patternedelectrodes 335 and 340 (derived from the same or different ECcompositions, described above) that are not electrically connected toeach other, are disposed contiguously with a planar surface of substrate345, as well as a first opposing surface (not shown) of dry PL 350provided from one or more suitable piezoelectric materials (describedabove). Dry DL-P 355 having (b) particles (not shown) is arrangedcontiguously with and in direct contact with opposing surface 360 of dryPL 350. The first opposing surface (not shown) of dry PL 350 is arrangedcontiguously with and in direct contact with non-electrically-connectedco-planar patterned electrodes 335 and 340 and constructed in such amanner that they are co-planar but not in electrical communication witheach other. Composite article 330 can be prepared by arranging the dryDL-P 355 from a suitable D-P composition (described above) to becontiguous with and in direct contact with opposing surface 360 of dryPL 350, and non-electrically-connected co-planar patterned electrodes335 and 340 can be formed from the same or different EC compositions ina desired co-planar pattern directly on an opposing surface (not shown)of dry PL 350. While it is not shown in FIG. 39, such a compositearticle can further comprise an outermost dry protective layer (asdescribed above) disposed over dry DL-P 355.

Still another embodiment according to the present invention is shown inFIG. 40. In composite article 365, non-electrically-connected (andinterdigitated) co-planar patterned electrodes 335 and 340 (derivedusing the same or different EC compositions, as described above) arearranged contiguously with planar surface 370 of substrate 345. Withinthe same plane, at least some gaps or some surface area in the sameplane, but between non-electrically-connected co-planar patternedelectrodes 335 and 340 (thus, between the interdigitated “fingers”) isfilled with dielectric material 375 provided from a D-P composition(described above) containing (b) particles. An opposing surface (notshown) of dry PL 350 is arranged contiguously with and in direct contactto both dielectric material 375 and both non-electrically-connectedco-planar patterned electrodes 335 and 340. While it is not shown inFIG. 40, an outermost dry protective layer (as described above) can bedisposed over opposing surface 378 of dry PL 350.

In another embodiment (not illustrated), similar to that shown in FIG.40, a continuous essentially uniform dry DL-P can be arranged to overlaytwo non-electrically-connected coplanar patterned electrodes (derivedfrom the same or different EC compositions, as described above) that arenot electrically connected but are arranged contiguously in the sameplane on an opposing surface of a dry PL. This embodiment can be furthermodified by putting a substrate (as described above) underneath thestructure (that is, underneath the two non-electrically-connectedco-planar patterned electrodes). Also, an outermost dry protective layer(as described above) can be disposed over the continuous dry DL-P.

In FIG. 41, composite article 380 comprises non-electrically-connectedco-planar patterned electrodes 390 and 395 derived from the same ordifferent EC-P compositions (for example, having the same or different(b) particles in the same or different amounts, as described above) thatare formed on opposing planar surface 385 of dry PL 350, but they arenot electrically connected, or in electrical communication, with eachother. Such composite articles can comprise more than two of suchnon-electrically-connected co-planar patterned electrodes on opposingplanar surface 385 of dry PL 350. Such composite articles can alsoinclude a substrate (not shown) under dry PL 350, an outermost dryprotective layer (not shown) disposed over non-electrically-connectedco-planar patterned electrodes 390 and 395, or both a substrate and anoutermost dry protective layer.

Yet another embodiment according to the present invention is shown inFIG. 42 wherein non-electrically-connected co-planar patternedelectrodes 390 and 395 (derived from the same or different EC-Pcomposition, as described above) are arranged contiguously with planarsurface 370 of substrate 345 and are also arranged contiguously with andin direct contact with an opposing surface (not shown) of dry PL 350. Noseparate dry dielectric layer is shown for this embodiment. However, anoutermost dry protective layer (not shown), that has dielectricproperties, can be disposed over an opposing surface of dry PL 350 ifdesired.

FIG. 45 shows composite article 440 having non-electrically-connectedco-planar patterned electrodes 445 and 450 in the shape of concentriccircles, disposed on opposing surface 455 of dry PL 460. At least one ofnon-electrically-connected co-planar patterned electrodes 445 and 450contains (b) particles.

Similarly, FIG. 46 shows composite article 465 havingnon-electrically-connected co-planar patterned electrodes 470 and 475 inthe serpentine shape, disposed on opposing surface 480 of dry PL 485. Atleast one of non-electrically-connected co-planar patterned electrodes470 and 475 contains (b) particles.

As described herein, the basic composite article according to thepresent invention comprises a PL in combination with an ECL-P, DL-P,ECL, or a pair of non-electrically-connected co-planar patternedelectrodes containing (b) particles, as long as each basic compositearticle comprises one of the components containing (b) particles. Suchcomposite article structure represents a basic “unit” that can beincorporated or formed into any of the devices described herein.However, it would be appreciated by one skilled in the art, and asillustrated in several Figures, that a composite article (orcorresponding device) according to the present invention could includeadditional PL's, ECL-P's, ECL's, and pairs of non-electrically-connectedco-planar patterned electrodes. Such composite articles can beconsidered to comprise a “stack” of the requisite layers or electrodesin order to achieve the desired function.

For example, a composite article according to the present invention cancomprise a basic stack comprising a PL having first and second opposingsurfaces, and first and second electrodes arranged oppositely on thefirst and second opposing surfaces, wherein at least one of theelectrodes is an ECL-P, or comprises at least one pair ofnon-electrically-connected co-planar patterned electrodes containing (b)particles. This composite article can further comprise a second PLarranged contiguously with one of the electrodes, and a third electrode(for example, an ECL-P, ECL, or pair of non-electrically-connectedco-planar electrodes) arranged contiguously on the opposing surface ofthe PL. Such alternating PL and electrode(s) on the opposing surface canbe arranged to any desired number, such as that the number of electrode“layers” in the composite article could be defined as (n+1), wherein nrepresents the number of PL's. Any or all of the electrode “layers” canbe uniform layers (ECL-P's or ECL's) or comprise one or more pairs ofnon-electrically-connected co-planar electrodes.

Similar composite articles can be designed with one or more DL-P's alongas there are a requisite number of PL's and electrode “layers.” A largenumber of different composite article designs can be developed by oneskilled in the art.

The present invention provides at least the following embodiments andcombinations thereof, but other combinations of features are consideredto be within the present invention as a skilled artisan would appreciatefrom the teaching of this disclosure:

1. A composite article comprising:

1) a first dry piezoelectric layer (first dry PL) comprising apiezoelectric material and having first and second opposing surfaces,and

2) a pair of non-electrically-connected co-planar patterned electrodesthat are arranged contiguously with at least one of the first and secondopposing surfaces of the first dry PL, each of the pair ofnon-electrically-connected co-planar patterned electrodes consistingessentially of:

(a) an electrically-conductive material; and

(b) particles distributed within the (a) electrically-conductivematerial, the (b) particles having a Young's modulus that is differentfrom the Young's modulus of the (a) electrically-conductive material byat least 10%, and which (b) particles have a d50 of at least 500 nm andup to and including 500 μm and a polydispersity coefficient of less thanor equal to 3, provided that the weight ratio of the (b) particles tothe (a) electrically-conductive material is at least 0.01:1 and up toand including 10:1, provided that the weight ratio of the (b) particlesto the (a) electrically-conductive material is at least 0.01:1 and up toand including 10:1;

provided that:

when each of the pair of non-electrically-connected co-planar patternedelectrodes is arranged adjacent to an insulating substrate, it exhibitsa resistivity of less than 10,000 ohms-cm, and

optionally, each of the pair of non-electrically-connected co-planarpatterned electrodes further includes (c) a binder material that isnon-electrically-conductive and has a weight average molecular weight ofat least 5,000.

2. The composite article of embodiment 1, wherein the (a)electrically-conductive material exhibits an electrical conductivity ofat least 2×10⁻⁴ S/m as measured by a Van der Pauw 4 probe method.

3. The composite article of embodiment 1 or 2, wherein the (a)electrically-conductive material comprises particles having a medianequivalent spherical volume diameter of at least 1 nm and up to andincluding 1000 μm and a polydispersity coefficient that is less than orequal to 2.

4. The composite article of any of embodiments 1 to 3, wherein the (a)electrically-conductive material comprises one or more of silver, gold,platinum, palladium, copper, nickel, titanium, and anelectrically-conductive form of carbon.

5. The composite article of any of embodiments 1 to 3, wherein the (a)electrically-conductive material is an electrically-conductive organicpolymer.

6. The composite article of any of embodiments 1 to 5, wherein the (a)electrically-conductive material consists essentially of silvernanoparticles having a d50 of less than or equal to 60 μm and a d90 ofless than or equal to 500 μm and a polydispersity that is less than orequal to 1.

7. The composite article of embodiment 6, wherein the silvernanoparticles have a d50 of at least 1 nm and up to and including 230 nmand a d90 of less than or equal to 300 μm.

8. The composite article of any of embodiments 1 to 7, wherein when eachof the pair of non-electrically-connected co-planar patterned electrodesis arranged contiguously with an insulating substrate, it exhibits aresistivity of less than 500 ohm-cm.

9. The composite article of any of embodiments 1 to 8, wherein when eachof the pair of non-electrically-connected co-planar patterned electrodesis arranged contiguously with an insulating substrate, it exhibits aresistivity of less than 150 ohm-cm.

10. The composite article of any of embodiments 1 to 9, wherein the (a)electrically-conductive material is present in an amount of at least 2weight % and up to and including 99 weight %, based on the total weightof each of the pair of non-electrically-connected co-planar patternedelectrodes.

11. The composite article of any of embodiments 1 to 10, wherein the (b)particles are composed of one or more polymeric materials.

12. The composite article of any of embodiments 1 to 11, wherein the (b)particles are composed of one or more inorganic materials.

13. The composite article of any of embodiments 1 to 12, wherein the (b)particles are solid and non-compressible.

14. The composite article of any of embodiments 1 to 13, wherein the (b)particles comprise one or more elastomeric polymers.

15. The composite article of any of embodiments 1 to 14, wherein the (b)particles are core-shell particles having a core that is comprised of amaterial different from the material comprising the shell.

16. The composite article of any of embodiments 1 to 15, wherein the (c)binder material is present and comprises one or more polyurethanes,acrylate polymers, polyvinyl acetals, or polyacrylate precursors to anacrylate polymer.

17. The composite article of any of embodiments 1 to 16, wherein the (c)binder material is present in an amount of at least 0.1 weight % and upto and including 10 weight %, based on the total weight of the at leastone dry ECL-P.

18. The composite article of any of embodiments 1 to 17, furthercomprising an insulating substrate and the pair ofnon-electrically-connected co-planar patterned electrodes are arrangedcontiguously between the insulating substrate and the first dry PL.

19. The composite article of embodiment 18, further comprising a firstdry electrically-conductive layer containing no (b) particles (first dryECL), which first dry ECL is arranged contiguously with the secondopposing surface of the first dry PL.

20. The composite article of embodiment 19, further comprising a firstdry electrically-conductive layer containing (b) particles (first dryECL-P) that is arranged contiguously with the first dry ECL that isarranged contiguously with the second opposing surface of the first dryPL.

21. The composite article of any of embodiments 1 to 20, furthercomprising dielectric material arranged in the same plane as and betweenthe pair of non-electrically-connected co-planar patterned electrodes.

22. The composite article of any of embodiments 1 to 21, wherein the (b)particles have a polydispersity coefficient that is less than or equalto 1.5.

23. The composite article of any of embodiments 1 to 22, wherein the (b)particles have a polydispersity coefficient that is less than or equalto 1.25.

24. The composite article of any of embodiments 1 to 23, wherein thefirst dry PL comprises beta phase polyvinylidene fluoride.

25. The composite article of any of embodiments 1 to 24, furthercomprising a second dry piezoelectric layer (second dry PL) comprising apiezoelectric material, which is arranged contiguously with anelectrically-conductive layer or a pair of non-electrically-connectedco-planar patterned electrodes that are arranged between the first dryPL and the second dry PL.

The following Examples are provided to illustrate the practice of thisinvention and are not meant to be limiting in any manner.

The median spherical volume diameters (d50) and other parameters forvarious (b) particles used in the Examples provided below are listed inTABLE IV.

TABLE IV PSD PSD PSD Standard PSD Poly- D50 Mean Deviation dispersity(b) Particle (μm) (μm) (μm) Coefficient Polybead ® 50 46.02 49.7017.3639 0.575 (Polysciences, Inc.) Polybead ® 100 91.31 106.11 55.93910.867 (Polysciences, Inc.) Polybead ® 200 201.43 232.42 98.7651 0.699(Polysciences, Inc.) MicroTouch ™ 800XF 7.75 8.09 3.4757 0.706 (MicroPowders, Inc.) MicroTouch ™ 800VF 10.74 11.37 5.3191 0.770 (MicroPowders, Inc.) MicroTouch ™ 800F 21.05 25.95 25.2926 1.603 (MicroPowders, Inc.) Ceramic microspheres W- 7.08 7.37 3.2082 0.716 210Ceramic microspheres W- 9.43 9.98 4.3572 0.718 410 Ceramic microspheresW- 10.71 11.38 5.0809 0.734 610 Nickel powder type 123 13.44 15.117.3233 0.797 Nickel powder type 525LD 16.49 16.71 5.7776 0.569 Nickelconductive flake 34.03 66.67 72.9515 1.800 HCA-1 Nickel flake fine water56.08 112.24 116.6275 1.709 grade (FWG)

The volume weighted frequency distribution of the particle size ofsamples was measured by methods known to those skilled in the art ofparticle sizing. Briefly, an amount of a particulate-containing samplewas dispersed in water with sonication for 2 minutes and then the volumeweighted frequency distribution of the particles in the dispersion wasmeasured using a Horiba Ltd. LA-920 particle size analyzer that obtainsa volume weighted frequency distribution of dispersed particles from0.05 μm to 2000 μm by static light scatter. All presented data are basedon volume weighted frequency distributions of the particles and theequivalent spherical diameter model. The term “volume weighted frequencydistribution” is used interchangeably here with “particle sizedistribution” and “PSD.”

The polydispersity coefficient for a volume weighted frequencydistribution is calculated from the mean particle size of thedistribution and the standard deviation (or the square root of thevariance) using the following formula:

${{Polydispersity}\mspace{14mu}{coefficient}} = \frac{1.654\sigma}{\left\langle d \right\rangle}$wherein σ is the standard deviation of the particle size distributionand (d) in this equation is the mean spherical volume diameter of thevolume weighted frequency distribution of the particle size. Calculationof the polydispersity coefficient of the volume weighted frequencydistribution of each type of particle shown in TABLE IV above. Thepolydispersity coefficient given in TABLE IV is greater than 0.05 forevery particle size distribution measured, indicating that the volumeweighted frequency distribution is not monodisperse. A polydispersitycoefficient greater than 0.05 indicates that many different particlesizes occur within the particle size distribution and that the observedvolume weighted frequency distribution has less than 90% of the sizedistribution lying within 5% of the median size.

A typical volume weighted frequency distribution for the particle sizeof the silver dispersion prepared and used in Comparative Example 1 isshown in FIG. 20. The median particle size of the volume weightedfrequency distribution for the silver dispersion used in ComparativeExample 1 is 0.1712 μm; the mean value of the frequency distribution is0.1876 μm; the standard deviation of the frequency distribution is0.1368 μm; and the polydispersity coefficient of the frequencydistribution is 1.2. According to the noted NIST Special Publication960-3 publication, the particle size distribution of the silverparticles indicates that Comparative Example 1 is a colloid and that theparticles are nanosized or nanoparticles. The NIST special PublicationSP 960-1 (cited above) defines mode as “the value of the variate forwhich the relative frequency in a series of observations reaches a localmaximum.” The variate is the equivalent spherical diameter particle sizein the volume weighted frequency distribution of the measured particlesize. An examination of the different volume weighted frequencydistributions for the different particles shows that more than one modeis often present in the frequency distribution. For example, the volumeweighted frequency distribution for the ECL Compositions flakemorphology (HCA-1 and FWG) for Comparative Examples 2-4 below show twomodes in the volume weighted frequency distribution of the particles.

Comparative Example 1: EC Composition Without (b) Particles

This aqueous silver nanoparticle dispersion was prepared as follows:

To a 1000 ml three-neck flask were added at 90° C. and under nitrogen,40 g of a 50 weight % solution of a polymer derived from acrylic acidand maleic acid (aim 50:50 molar ratio and M_(w) of 3,000, availablefrom Sigma-Aldrich) and 240 g of a 50% aqueous diethanolamine solution.To this solution, 120 g of a 54.75 weight % aqueous silver nitratesolution was added dropwise over 150 minutes. The resulting reactiondispersion was stirred overnight before being cooled to roomtemperature. The dispersion was then sonicated for 20 minutes and solidswere permitted to settle. After the supernatant was decanted off, theconcentrated dispersion of silver nanoparticles was dialyzed overnightand then centrifuged for 2 hours at 7000 rpm. The resulting silvernanoparticle slurry was then re-dispersed in water, sonicated, andfiltered through a 1 μm filter. This silver nanoparticle dispersion isalso referred to herein as the “silver colloid.” The aqueous silvernanoparticle dispersion at >70 weight % was then mixed with 0.5 weight %of Acrysol™ RM-12 W, a polyurethane resin rheology modifier solution inwater using a FlackTek Speedmixer™ DAC 150 speedmixer for 1-3 minutes ata speed >1500 rpm to provide the desired aqueous silver nanoparticledispersion with binder material. Acrysol™ RM-12 W contains 19 weight %of polyurethane resin rheology modifier solids and the polyurethaneresin rheology modifier in Acrysol™ RM-12 W was used as a (c) bindermaterial.

A typical volume weighted frequency distribution for the particle sizeof the silver dispersion prepared and used in Comparative Example 1 isshown in FIG. 20. According to the noted NIST Special Publication 960-3publication, the particle size distribution of the silver particlesindicates that Comparative Example 1 is a colloid and that the particlesare nanosized or nanoparticles.

The following “wet” EC-P compositions prepared according to the presentinvention are described in Invention Examples 1-21. TABLE V belowprovides details as to the amounts of weight % solids of (a)electrically-conductive material, weight % solids of a water-soluble orwater-dispersible (c) polyurethane resin binder material, weight %solids of (b) particles, the weight % of the (d) solvent medium, and theparticle d50 in micrometers in the EC-P compositions of InventionExamples 1-20. In addition, TABLE V shows the calculated weight ratio of(b) particles to the (a) silver nanoparticles.

Invention Example 1: EC-P Composition

3 weight % of spherical crosslinked poly(styrene-co-divinylbenzene-co-ethylvinyl benzene) (b) particles (d50 particle size of 46pin) was added to a weighed amount of the Comparative Example 1 ECcomposition described above before mixing using the FlackTek Speedmixer™DAC 150 speedmixer.

Invention Example 2: EC-P Composition

7 weight % of spherical crosslinked poly(styrene-co-divinylbenzene-co-ethylvinyl benzene) (b) particles (d50 particle size of 91μm) was added to a weighed amount of the Comparative Example 1 ECcomposition described above before mixing using the FlackTek Speedmixer™DAC 150 speedmixer.

Invention Example 3: EC-P Composition

7 weight % of spherical crosslinked poly(styrene-co-divinylbenzene-co-ethylvinyl benzene) (b) particles (d50 particle size of 201μm) was added to a weighed amount of the Comparative Example 1 ECcomposition described above before mixing using the FlackTek Speedmixer™DAC 150 speedmixer.

The typical volume weighted frequency distribution for the particle sizeof crosslinked polystyrene particles used in Invention Examples 1-3 areshown in FIG. 21. The crosslinked polystyrene resin particles arecomprised of beads of polystyrene resin (copolymer of styrene anddivinylbenzene/ethylvinyl benzene mixture) as described in U.S. Pat. No.7,441,717 (Majka et al.) and U.S. Pat. No. 5,478,705 (Caekai et al.) andare notated as Polybead® 50, Polybead® 100, and Polybead® 200 in theTABLE IV above. The preparation of such crosslinked polystyreneparticles and other resin particles that are useful in the presentinvention is described in the noted U.S. Pat. No. 5,478,705 thedisclosure of which is hereby incorporated by reference in its entirety.

Invention Example 4: EC-P Composition

7.5 weight % of solid alkali alumino silicate ceramic microsphere (b)particles (3M Ceramic Microspheres White Grade W-210, having a d50particle size of 7 μm) was added to a weighed amount of the ComparativeExample 1 EC composition described above before mixing using theFlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 5: EC-P Composition

7.5 weight % of solid alkali alumino silicate ceramic microsphere (b)particles (3M Ceramic Microspheres White Grade W-410, having a d50particle size of 9.4 μm) was added to a weighed amount of theComparative Example 1 EC composition described above before mixing usingthe FlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 6: EC-P Composition

7.5 weight % of solid alkali alumino silicate ceramic microsphere (b)particles (3M Ceramic Microspheres White Grade W-610, having a d50particle size of 10.7 μm) was added to a weighed amount of theComparative Example 1 EC composition described above before mixing usingthe FlackTek Speedmixer™ DAC 150 speedmixer.

The typical volume weighted frequency distribution for the particle sizeof spherical alumino-silicate particles used in Invention Examples 4-6are shown in FIG. 23. The spherical alumino-silicate ceramic particlesare commercially available particles (3M ceramic microspheres WhiteGrades W-210, W-410, and W-610) supplied by 3M Energy and AdvanceMaterials Division, St. Paul, Minn.

Invention Example 7: EC-P Composition

1 weight % of spherical crosslinked aliphatic polyurethane (b) particles(Micro Powders, Inc. MicroTouch™ 850 XF with an effective d50 particlesize of 7.75 μm) was added to a weighed amount of the ComparativeExample 1 EC composition described above before mixing using theFlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 8: EC-P Composition

2 weight % of spherical crosslinked aliphatic polyurethane (b) particles(Micro Powders, Inc. MicroTouch™ 850 XF with an effective d50 particlesize of 7.75 μm) was added to a weighed amount of the ComparativeExample 1 EC composition described above before mixing using theFlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 9: EC-P Composition

7.5 weight % of spherical crosslinked aliphatic polyurethane (b)particles (Micro Powders, Inc. MicroTouch™ 850 XF with an effective d50particle size of 7.75 μm) was added to a weighed amount of theComparative Example 1 EC composition described above before mixing usingthe FlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 10: EC-P Composition

12.5 weight % of spherical crosslinked aliphatic polyurethane (b)particles (Micro Powders, Inc. MicroTouch™ 850 XF with an effective d50particle size of 7.75 μm) was added to a weighed amount of theComparative Example 1 EC composition described above before mixing usingthe FlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 11: EC-P Composition

7 weight % of spherical crosslinked aliphatic polyurethane (b) particles(Micro Powders, Inc. MicroTouch™ 800 VF with an effective d50 particlesize of 12-16 μm) was added to a weighed amount of the ComparativeExample 1 EC composition described above before mixing using theFlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 12: EC-P Composition

7 weight % of spherical crosslinked aliphatic polyurethane (b) particles(Micro Powders, Inc. MicroTouch™ 800F with an effective d50 particlesize of 21 μm) was added to a weighed amount of the Comparative Example1 EC composition described above before mixing using the FlackTekSpeedmixer™ DAC 150 speedmixer.

The typical volume weighted frequency distribution for the particle sizeof spherical crosslinked aliphatic polyurethane particles used inInvention Examples 7-12 are shown in FIG. 22. The spherical crosslinkedaliphatic polyurethane particles are commercially available particles(MicroTouch™ 800F, 800VF, and 850XF) supplied by Micro Powders, Inc.Tarrytown, N.Y.

Invention Example 13: EC-P Composition

5 weight % of low density filamentary powder nickel (b) particles(Novamet, Nickel Powder 525LD, with an effective D50 particle size of16.5 μm in size) was added to a weighed amount of the ComparativeExample 1 EC composition described above before mixing using theFlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 14: EC-P Composition

5 weight % of irregular platelet nickel (b) particles (Novamet,Conductive Nickel Flake HCA-1, with an effective d50 particle size of 34μm and an aspect ratio approaching 20:1) was added to a weighed amountof the Comparative Example 1 EC composition described above beforemixing using the FlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 15: EC-P Composition

5 weight % of platelet nickel (b) particles (Novamet, Nickel flake-FineWater Grade with an effective d50 of 56 μm) was added to a weighedamount of the Comparative Example 1 EC composition described abovebefore mixing using the FlackTek Speedmixer™ DAC 150 speedmixer.

Invention Example 16: EC-P Composition

5 weight % of spiky nickel (b) particles (Novamet, Nickel Powder Type123 with an effective d50 particle size of 13 μm) was added to a weighedamount of the Comparative Example 1 EC composition described abovebefore mixing using the FlackTek Speedmixer™ DAC 150 speedmixer.

The typical volume weighted frequency distribution for the particle sizeof different types of nickel containing particles used in InventionExamples 13-16 are shown in FIG. 24. The spherical nickel particles typeT123 were commercially available particles manufactured by Vale CanadaLimited and supplied by Novamet Specialty Products Corporation, Lebanon,Tenn. The type 525LD nickel particles, the type HCA-1 nickel flakeparticles and the fine water grade (FWG) nickel flake particles weresupplied by Novamet Specialty Products Corporation, Lebanon, Tenn.

Invention Example 17: EC-P Composition

An aqueous silver nanoparticle dispersion with >70 weight % silvernanoparticle solids as described above for Comparative Example 1 (butwith no polyurethane added) was mixed with 3.5 weight % of poly(vinylpyrrolidone) (c) binder material (K30, M_(w) of 40,000) and 12 weight %of solid alkali alumino silicate ceramic microsphere (b) particles (3MCeramic Microspheres White Grade W-410 with an effective d50 particlesize of 9.4 μm) using the FlackTek Speedmixer™ DAC 150 speedmixer for1-3 minutes at a speed >1500 rpm.

Invention Example 18: EC-P Composition

An aqueous silver nanoparticle dispersion with >70 weight % silvernanoparticle solids as described above for Comparative Example 1 (butwith no polyurethane added) was mixed with 3 weight % ofpoly(3,4-ethylenedioxythiophene) polystyrene sulfonate (c) bindermaterial (Baytron™ PHC V4) and 7 weight % of solid alkali aluminosilicate ceramic microsphere (b) particles (3M Ceramic MicrospheresWhite Grade W-410 with an effective d50 particle size of 9.4 μm) usingthe FlackTek Speedmixer™ DAC 150 speedmixer for 1-3 minutes at aspeed >1500 rpm.

Invention Example 19: EC-P Composition

An aqueous silver nanoparticle dispersion with >70 weight % silvernanoparticle solids as described above for Comparative Example 1 (butwith no polyurethane added) was mixed with 2 weight % of athermoplastic, polyvinyl butyral resin (c) binder material (Butvar™ 76)and 7 weight % of solid alkali alumino silicate ceramic microsphere (b)particles (3M Ceramic Microspheres White Grade W-410 with an effectived50 particle size of 9.4 μm) using the FlackTek Speedmixer™ DAC 150speedmixer for 1-3 minutes at a speed >1500 rpm.

Invention Example 20: EC-P Composition

An aqueous silver nanoparticle dispersion with >70 weight % silvernanoparticle solids as described above for Comparative Example 1 (butwith no polyurethane added) was mixed with 4 weight % of a radiationcurable rheology modifier, ethoxylated trimethylolpropane triacrylate(Sartomer SR415) and 0.4 weight % of a free radical initiator,4,4′-azobis(4-cyanovaleric Acid) (Vazo-68) used to form a (c) bindermaterial, and 6 weight % of solid alkali alumino silicate ceramicmicrosphere (b) particles (3M Ceramic Microspheres White Grade W-410with an effective d50 particle size of 9.4 μm) using the FlackTekSpeedmixer™ DAC 150 speedmixer for 1-3 minutes at a speed >1500 rpm.

Invention Example 21: EC-P Composition

This invention example demonstrates the ability to use a different (a)electrically-conductive material other than the silver nanoparticlesdescribed above in Invention Examples 1-20.

A conductive polymer dispersed in water,poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (Baytron™ PHC V4)was used as the (a) electrically-conductive material. This polymer alsoserved as the (c) binder material and was mixed with ethylene glycol andsolid alkali alumino silicate ceramic microsphere particles (3M CeramicMicrospheres White Grade W-410 with an effective d50 particle size of9.4 μm) using the FlackTek Speedmixer™ DAC 150 speedmixer for 1-3minutes at >1500 rpm. The ethylene glycol functioned as a co-solvent andsecondary rheology modifier in the ECL-P composition. The weight ratiowas 83.5:9:7.5 for the poly(3,4-ethylenedioxythiophene) polystyrenesulfonate: ethylene glycol: solid alkali alumino silicate ceramicmicrosphere particles. The resulting EC-P composition contained about82.5 weight % water as the (d) solvent medium and the weight ratio ofthe (b) solid particles to the (a) electrically-conductive polymer was7:1.

The following comparative examples demonstrate the need for the (a)electrically-conductive material to have a Young's modulus differentfrom that of the (b) particles. In these examples, commerciallyavailable “inks” containing silver nanoparticles of various sizes as the(a) electrically-conductive materials were mixed to show the necessityof different Young's modulus, not solely particle size variations. Thesecomparative examples are outside of the present invention.

Comparative Example 2: EC Composition

An aqueous electrically-conductive silver ink, (NovaCentrix HPS-030LV)comprising nanometer-sized (a) electrically-conductive particles wasmixed with an aqueous electrically-conductive silver ink (NovaCentrixHPS-021LV) comprising micrometer-sized flake (b) particles in an amountof 1.5 grams of (b) particles to 0.5 grams of (a)electrically-conductive particles to provide a weight ratio of 75:25 (h)to (a) electrically-conductive particles. The NovaCentrix HPS-030LV andHPS-021LV were used as received and no (c) binder material was added tothe dispersion. The resulting dispersion was mixed in the FlackTekSpeedmixer™ DAC 150 speedmixer for 1-3 minutes at a speed >1500 rpm.

Comparative Example 3: EC Composition

An aqueous electrically-conductive silver ink, (NovaCentrix HPS-030LV)comprising nanometer-sized (a) electrically-conductive particles wasmixed with an aqueous electrically-conductive silver ink (NovaCentrixHPS-021LV) comprising micrometer-sized flake (b) particles in an amountof 1 gram of (b) particles to 1 gram of (a) electrically-conductiveparticles to provide a weight ratio of 50:50 (b) particles to (a)electrically-conductive particles. The NovaCentrix HPS-030LV andHPS-021LV were used as received and no (c) binder material was added tothe dispersion. The resulting dispersion was mixed in the FlackTekSpeedmixer™ DAC 150 speedmixer for 1-3 minutes at a speed >1500 rpm.

Comparative Example 4: EC Composition

An aqueous electrically-conductive silver ink, (NovaCentrix HPS-030LV)comprising nanometer-sized (a) electrically-conductive particles wasmixed with an aqueous electrically-conductive silver ink (NovaCentrixHPS-021LV) comprising micrometer-sized flake (b) particles in an amountof 0.5 gram of (b) particles to 1.5 grams of (a) electrically-conductiveparticles to provide a weight ratio of 25:75 (b) to (a) particles. TheNovaCentrix HPS-030LV and HPS-021LV were used as received and no (c)binder material was added to the dispersion. The resulting dispersionwas mixed in the FlackTek Speedmixer™ DAC 150 speedmixer for 1-3 minutesat a speed >1500 rpm.

FIG. 25 shows the volume weighted frequency distribution for theparticle size of the two commercially available silver inks produced byNovamet and used in Comparative Examples 2-4. The measured data from theparticle size distribution for these silver inks are a median of 0.2918μm; mean of 1.3452 μm; standard deviation of 1.4826 μm; and apolydispersity coefficient of 1.81 for the HPS-021LV HS ink; and amedian of 0.1656 μm; mean of 0.2014 μm; standard deviation of 0.1699 μm;and a polydispersity coefficient of 1.39 for the HPS-030LV HS ink.

The following TABLE V summarizes the compositional features and amountsfor the EC-P compositions of Invention Examples 1-21.

TABLE V Solid weight % Solid Weight of (a) Silver weight % Solid % (b)Nanoparticles of (c) Weight % of (d) Particles (b) to (a) Invention orconductive Binder of (b) Solvent d50 Weight Example media MaterialParticles Medium (μm) Ratio Type of (b) Particles 1 72.4 0.1 3 24.5 460.041 3 weight % of spherical crosslinked poly(styrene- co-divinylbenzene-co-ethylvinyl benzene (Polybead ® 50), 0.5% Acrysol ™ RM-12W 269.4 0.1 7 23.5 91 0.101 7 weight % of spherical crosslinkedpoly(styrene- co-divinyl benzene-co-ethylvinyl benzene (Polybead ® 100),0.5% Acrysol ™ RM-12W 3 69.4 0.1 7 23.5 201 0.101 7 weight % ofspherical crosslinked poly(styrene- co-divinyl benzene-co-ethylvinylbenzene (Polybead ® 200), 0.5% Acrysol ™ RM-12W 4 69 0.1 7.5 23.4 70.109 7.5 weight % of solid alkali alumino silicate ceramic microsphereparticles (3M Ceramic Microspheres White Grade W-210), 0.5% Acrysol ™RM-12W 5 69 0.1 7.5 23.4 9.4 0.109 7.5 weight % of solid alkali aluminosilicate ceramic microsphere particles (3M Ceramic Microspheres WhiteGrade W-410), 0.5% Acrysol ™ RM-12W 6 69 0.1 7.5 23.4 10.7 0.109 7.5weight % of solid alkali alumino silicate ceramic microsphere particles(3M Ceramic Microspheres White Grade W-610), 0.5% Acrysol ™ RM-12W 773.9 0.1 1 24.8 7.75 0.027 1 weight % of crosslinked spherical aliphaticpolyurethane particles (Micro Powders, Inc. MicroTouch ™ 850XF), 0.5%Acrysol ™ RM-12W 8 73 0.1 2 24.8 7.75 0.027 2 weight % of crosslinkedspherical aliphatic polyurethane micron-sized particles (Micro Powders,Inc. MicroTouch ™ 850XF), 0.5% Acrysol ™ RM-12W 9 68.6 0.1 7.5 23.8 7.750.109 7.5 weight % of crosslinked spherical aliphatic polyurethaneparticles (Micro Powders, Inc. MicroTouch ™ 850XF), 0.5% Acrysol ™RM-12W 10 64.9 0.1 7 23.9 7.75 0.108 12.5 weight % of crosslinkedspherical aliphatic polyurethane particles (Micro Powders, Inc.MicroTouch ™ 850XF), 0.5% Acrysol ™ RM-12W 11 69 0.1 7 23.9 10.7 0.101 7weight % of crosslinked spherical aliphatic polyurethane particles(Micro Powders, Inc. MicroTouch ™ 800VF), 0.5% Acrysol ™ RM-12W 12 690.1 7 23.9 21 0.101 7 weight % of cross-linked spherical aliphaticpolyurethane particles (Micro Powders, Inc. MicroTouch ™ 800F), 0.5%Acrysol ™ RM-12W 13 70.5 0.1 5 24.4 16.5 0.071 5 weight % of low densityfilamentary powder nickel particles (Novamet, Nickel Powder 525LD), 0.5%Acrysol ™ RM-12W 14 70.5 0.1 5 24.4 34 0.071 5 weight % of irregularplatelet nickel particles (Novamet, Conductive Nickel Flake HCA-1), 0.5%Acrysol ™ RM-12W 15 70.5 0.1 5 24.4 56 0.071 5 weight % of plateletnickel particles (Novamet, Nickel flake Fine Water), 0.5% Acrysol ™ RM-12W 16 70.5 0.1 5 24.4 13 0.071 5 weight % of spiky nickel particles(Novamet, Nickel Powder Type 123), 0.5% Acrysol ™ RM- 12W 17 63 1.05 1224 9.4 0.190 3.5 weight % of a (d) poly(vinyl pyrrolidone) K30, M_(w) of40,000) and 12 weight % of solid alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410) 1867.5 0.036 7 24.6 9.4 0.103 3 weight % of (d) poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (Baytron ™ PHC V4) and 7weight % of solid alkali alumino silicate ceramic microsphere particles(3M Ceramic Microspheres White Grade W-410) 19 68.25 0.2 7 24.6 9.40.103 2 weight % of a (d) thermoplastic, poly(vinyl butyral) resin(Butvar ™ 76) and 7 weight % of solid alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410) 2089.6 4.4 6 4 9.4 0.067 4 weight % of a radiation curable ethoxylatedtrimethylolpropane triacrylate (Sartomer SR415)) and 0.4 weight % ofinitiator, 4,4′-azobis(4- cyanovaleric acid (Vazo-68) to form (d)polymer and 6 weight % of solid alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410) 21 1 97.5 82.5 9.4 7.5 7.5 weight % of solid alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410)

The EC and EC-P compositions described above were used to formelectrically-conductive layers in multilayer composite articles. Theamounts of the components in those layers are shown in TABLE VI below.

The multilayer composite articles were prepared in the followingExamples to have a dry piezoelectric layer (dry PL) (as shown in TABLEVII below) and one or more electrically-conductive layers as“electrodes,” one of which layers was prepared using an EC-P compositionalso identified in TABLE VII below. In Comparative Examples 5-8 andInvention Examples 23-43, the dry PL already had a preformedelectrically-conductive layer (electrode) on it before the EC-Pcomposition was applied. The poly(vinylidene fluoride) PL was secured ona coating block while the specific EC or EC-P composition was appliedusing a pipette and the droplet(s) were spread evenly on the dry PLplanar surface using a Meyer rod to provide a wet coverage of 22 μm to86 μm. For Invention Example 44, a nickel electrode layer was preformedon the lead zirconium titanate ceramic planar surface by sputtering.Invention Example 44 was prepared by securing the ceramic on a coatingblock while the specific EC-P composition was applied using a pipetteand the droplet(s) were spread evenly on the PL planar surface using aMeyer rod to provide a wet coverage of 22 μm.

TABLE VI Solid weight % of (a) Silver Nanoparticles Solid weight SolidWeight (b) Particles Invention or conductive % of (c) % of (b) d50Example media Polymer Particles (μm) Type of (b) Particles 1 96 0.1 3.946 3 weight % of spherical crosslinked poly(styrene-co-divinylbenzene-co-ethylvinyl benzene (Polybead-50), 0.5% Acrysol ™ RM-12W 290.7 0.1 9.2 91 7 weight % of spherical crosslinkedpoly(styrene-co-divinyl benzene-co-ethylvinyl benzene (Polybead-100),0.5% Acrysol ™ RM-12W 3 90.7 0.1 9.2 201 7 weight % of sphericalcrosslinked poly(styrene-co-divinyl benzene-co-ethylvinyl benzene(Polybead-200), 0.5% Acrysol ™ RM-12W 4 90.1 0.1 9.8 7 7.5 weight % ofsolid alkali alumino silicate ceramic microsphere particles (3M CeramicMicrospheres White Grade W-210), 0.5% Acrysol ™ RM-12W 5 90.1 0.1 9.89.4 7.5 weight % of solid alkali alumino silicate ceramic microsphereparticles (3M Ceramic Microspheres White Grade W-410), 0.5% Acrysol ™RM-12W 6 90.1 0.1 9.8 10.7 7.5 weight % of solid alkali alumino silicateceramic microsphere particles (3M Ceramic Microspheres White GradeW-610), 0.5% Acrysol ™ RM-12W 7 98.9 0.1 1 7.75 1 weight % ofcrosslinked spherical aliphatic polyurethane particles (Micro Powders,Inc. MicroTouch ™ 850XF), 0.5% Acrysol ™ RM-12W 8 97.4 0.1 2.5 7.75 2weight % of crosslinked spherical aliphatic polyurethane micron-sizedparticles (Micro Powders, Inc. MicroTouch ™ 850XF), 0.5% Acrysol ™RM-12W 9 90.9 0.1 9.8 7.75 7.5 weight % of crosslinked sphericalaliphatic polyurethane particles (Micro Powders, Inc. MicroTouch ™850XF), 0.5% Acrysol ™ RM-12W 10 83.9 0.1 16 7.75 12.5 weight % ofcrosslinked spherical aliphatic polyurethane particles (Micro Powders,Inc. MicroTouch ™ 850XF), 0.5% Acrysol ™ RM-12W 11 90.7 0.1 9.2 10.7 7weight % of crosslinked spherical aliphatic polyurethane particles(Micro Powders, Inc. MicroTouch ™ 800VF), 0.5% Acrysol ™ RM-12W 12 90.70.1 9.2 21 7 weight % of cross-linked spherical aliphatic polyurethaneparticles (Micro Powders, Inc. MicroTouch ™ 800F), 0.5% Acrysol ™ RM-12W13 93.3 0.1 6.6 16.5 5 weight % of low density filamentary powder nickelparticles (Novamet, Nickel Powder 525LD), 0.5% Acrysol ™ RM-12W 14 93.30.1 6.6 34 5 weight % of irregular platelet nickel particles (Novamet,Conductive Nickel Flake HCA-1), 0.5% Acrysol ™ RM-12W 15 93.3 0.1 6.6 565 weight % of platelet nickel particles (Novamet, Nickel flake FineWater), 0.5% Acrysol ™ RM-12W 16 93.3 0.1 6.6 13 5 weight % of spikynickel particles (Novamet, Nickel Powder Type 123), 0.5% Acrysol ™RM-12W 17 83.3 1.0 15.7 9.4 3.5 weight % of a (d) poly(vinylpyrrolidone) K30, M_(w) of 40,000) and 12 weight % of solid alkalialumino silicate ceramic microsphere particles (3M Ceramic MicrospheresWhite Grade W-410) 18 90.5 0.036 9.4 9.4 3 weight % of (d)poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (Baytron ™ PHCV4) and 7 weight % of solid alkali alumino silicate ceramic microsphereparticles (3M Ceramic Microspheres White Grade W-410) 19 90.5 0.2 9.39.4 2 weight % of a (d) thermoplastic, poly(vinyl butyral) resin(Butvar ™ 76) and 7 weight % of solid alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410) 2089.6 4.4 6 9.4 4 weight % of a radiation curable ethoxylatedtrimethylolpropane triacrylate (Sartomer SR415)) and 0.4 weight % ofinitiator, 4,4′-azobis(4-cyanovaleric acid (Vazo-68) to form (d) polymerand 6 weight % of solid alkali alumino silicate ceramic microsphereparticles (3M Ceramic Microspheres White Grade W-410) 21 5.7 51.4 42.99.4 7.5 weight % of solid alkali alumino silicate ceramic microsphereparticles (3M Ceramic Microspheres White Grade W-410)

TABLE VII ECL or ECL-P Wet TABLE I Thickness Example EC or EC-PComposition Composition PL Material (μm) Comparative 5 Silvernanoparticles; Acrysol ™ RM-12W; water [no Comparative 1 28 μm PVDF;Ag-electroded 22 (b) particles] (1-1004346-0 TE Connectivity) Invention22 Silver nanoparticles; Acrysol ™ RM-12W; d50 of 46 μm Invention 1 28μm PVDF; Ag-electroded 22 crosslinked polystyrene particles; water(1-1004346-0 TE Connectivity) Invention 23 Silver nanoparticles;Acrysol ™ RM-12W; d50 of 91 μm Invention 2 28 μm PVDF; Ag-electroded 86crosslinked polystyrene particles; water (1-1004346-0 TE Connectivity)Invention 24 Silver nanoparticles; Acrysol ™ RM-12W; d50 of Invention 328 μm PVDF; Ag-electroded 86 201 μm crosslinked polystyrene particles;water (1-1004346-0 TE Connectivity) Invention 25 Silver nanoparticles;Acrysol ™ RM-12W; Invention 4 28 μm PVDF; Ag-electroded 22 d50 of 7 μmalumino silicate ceramic (1-1004346-0 TE microspheres; waterConnectivity) Invention 26 Silver nanoparticles; Acrysol ™ RM-12W; d50of 9.4 μm Invention 5 28 μm PVDF; Ag-electroded 22 alumino silicateceramic microspheres; water (1-1004346-0 TE Connectivity) Invention 27Silver nanoparticles; Acrysol ™ RM-12W; d50 of Invention 6 28 μm PVDF;Ag-electroded 22 10.4 μm alumino silicate ceramic microspheres;(1-1004346-0 TE Connectivity) water Invention 28 Silver nanoparticles;Acrysol ™ RM-12W; 1 weight Invention 7 28 μm PVDF; Ag-electroded 22 %d50 of 7.75 μm crosslinked aliphatic polyurethane (1-1004346-0 TEConnectivity) microspheres; water Invention 29 Silver nanoparticles;Acrysol ™ RM-12W; 2 weight Invention 8 28 μm PVDF; Ag-electroded 22 %d50 of 7.75 μm crosslinked aliphatic polyurethane (1-1004346-0 TEConnectivity) microspheres; water Invention 30 Silver nanoparticles;Acrysol ™ RM-12W; 7.5 weight Invention 9 28 μm PVDF; Ag-electroded 22 %d50 of 7.75 μm crosslinked aliphatic polyurethane (1-1004346-0 TEConnectivity) microspheres; water Invention 31 Silver nanoparticles;Acrysol ™ RM-12W; 12.5 Invention 10 28 μm PVDF; Ag-electroded 22 weight% d50 of 7.75 μm crosslinked aliphatic (1-1004346-0 TE Connectivity)polyurethane microspheres; water Invention 32 Silver nanoparticles;Acrysol ™ RM-12W; d50 of Invention 11 28 μm PVDF; Ag-electroded 22 10.7μm crosslinked aliphatic polyurethane (1-1004346-0 TE Connectivity)microspheres; water Invention 33 Silver nanoparticles; Acrysol ™ RM-12W;d50 of 21 μm Invention 12 28 μm PVDF; Ag-electroded 22 crosslinkedaliphatic polyurethane microspheres; (1-1004346-0 TE Connectivity) waterInvention 34 Silver nanoparticles; Acrysol ™ RM-12W; d50 of 16 μmInvention 13 28 μm PVDF; Ag-electroded 22 of low density filamentarynickel powder; water (1-1004346-0 TE Connectivity) Invention 35 Silvernanoparticles; Acrysol ™ RM-12W; d50 of 34 μm Invention 14 28 μm PVDF;Ag-electroded 22 of irregular platelet nickel particles; water(1-1004346-0 TE Connectivity) Invention 36 Silver nanoparticles;Acrysol ™ RM-12W; d50 of 56 μm Invention 15 28 μm PVDF; Ag-electroded 22fine flake nickel platelets; water (1-1004346-0 TE Connectivity)Invention 37 Silver nanoparticles; Acrysol ™ RM-12W; d50 of 13 μmInvention 16 28 μm PVDF; Ag-electroded 22 spiky nickel particles; water(1-1004346-0 TE Connectivity) Invention 38 Silver nanoparticles;poly(vinyl pyrrolidone) K30; Invention 17 28 μm PVDF; Ag-electroded 22d50 of 9.4 μm alumino silicate ceramic (1-1004346-0 TE Connectivity)microspheres; water Invention 39 Silver nanoparticles; poly(3,4-Invention 18 28 μm PVDF; Ag-electroded 22 ethylenedixoythiophene)polystyrene sulfonate; d50 (1-1004346-0 TE Connectivity) of 9.4 μmalumino silicate ceramic microspheres; water Invention 40 Silvernanoparticles; thermoplastic poly(vinyl Invention 19 28 μm PVDF;Ag-electroded 22 butyral) resin; d50 of 9.4 μm alumino silicate(1-1004346-0 TE Connectivity) ceramic microspheres; water Invention 41Silver nanoparticles; ethoxylated trimethylolpropane Invention 20 28 μmPVDF; Ag-electroded 22 triacrylate; 4,4′-azobis(4-cyanovaleric acid);d50 of (1-1004346-0 TE Connectivity) 9.4 μm alumino silicate ceramicmicrospheres; water Invention 42 Poly(3,4-ethylenedixoythiophene)polystyrene Invention 21 28 μm PVDF; Ag-electroded 22 sulfonate;ethylene glycol; d50 of 9.4 μm alumino (1-1004346-0 TE Connectivity)silicate ceramic microspheres; water Comparative 6 NovaCentrixHPS-021LV:HPS-030LV (75:25 Comparative 2 28 μm PVDF; Ag-electroded 22weight ratio) (1-1004346-0 TE Connectivity) Comparative 7 NovaCentrixHPS-021LV:HPS-030LV (50:50 Comparative 3 28 μm PVDF; Ag-electroded 22weight ratio) (1-1004346-0 TE Connectivity) Comparative 8 NovaCentrixHPS-021LV:HPS-030LV (25:75 Comparative 4 28 μm PVDF; Ag-electroded 22weight ratio) (1-1004346-0 TE Connectivity) Invention 43 Silvernanoparticles; Acrysol ™ RM-12W; d50 of 9.4 μm Invention 5 110 μm PVDF;Ag-electroded 22 alumino silicate ceramic microspheres; water(3-1004347-0 TE Connectivity) Invention 44 Silver nanoparticles;Acrysol ™ RM-12W; d50 of 9.4 μm Invention 5 Lead Zirconate Titanate 22alumino silicate ceramic microspheres; water (type 5H; Navy Type VI)

Measurement of Electrical Properties of Composite Electrodes:

To characterize the range of useful electrical properties for thecomposite articles described above, the electrical resistivity ofcomposite electrodes prepared using the EC or EC-P compositionsdescribed above were measured using the known Van der Pauw technique.This technique was typically carried out for each EC or EC-P compositionafter it had been coated onto a printed circuit board (PCB) substrateand dried to form an article comprising a thin continuous solid layer ofan electrode. The PCB substrate had 4 electrode pads on its planarsurface that were evenly spaced around the circumference of a circle.Each EC or EC-P composition was coated onto the PCB planar surface sothat the edge of the coated region contacted the electrode pads on thePCB substrate, thus providing a solid continuous planar electrode regionwhose electrical properties could be measured. The ohmic behavior ofeach electrical contact between the electrode and the 4 electrode padswas verified before measurement of electrical resistivity by examiningthe current-voltage (I-V) characteristics of the contacts to ensure thatthe I-V characteristics were linear across the voltage range used in thesubsequent electrical measurements. The thickness of the electrode onthe PCB substrate was measured using a Mitotoyo model LGB2-0105L gaugehead with a model EF-PH display. The current for the electricalmeasurements was supplied by a Keithley model 224 programmable currentsource and voltages were measured using a Keithley model 2100 6 1/2digital multimeter. The electrical resistivity of each formed electrodewas calculated from the measured current and voltages as described by L.J. Van der Pauw in Phillips Technical Review volume 20(8), pages220-224, 1958/1959.

d33 Measurements:

The composite articles of Comparative Example 5-9 and Inventive Examples22 through 46 were placed in an experimental apparatus to determine thed₃₃ piezoelectric charge coefficient. Measurement of d₃₃ of eachcomposite article and devices with composite electrodes was performedaccording to the Berlincourt method as described by Stewart and Cain (M.G. Cain (ed.), Characterisation of Ferroelectric Bulk Materials and ThinFilms, 37, Springer Series in Measurement Science and Technology 2, DOI:10.1007/978-1-4020-9311-1_3, © Queen's Printer and Controller of HMSO2014 Chapter 2 pp 37-64). The electronic charge generated by eachcomposite article when it was subjected to an oscillating stress wascollected using a pair of 12.5 mm diameter cylindrical steel electrodesthat were in contact with opposing surfaces of the composite article andconnected to an electrometer (Keithley 617) that was used to measure theelectronic charge generated by the composite article in units ofcoulombs and the output of the electrometer was connected to a digitaloscilloscope (Tektronix 2024B) for data recording. The oscillatingstress on the composite article was applied by an insulating anvil thatwas connected to a piezoelectric ceramic stack. The oscillatingdisplacement of the piezoelectric stack used to generate the oscillatingstress on the composite article was produced by driving thepiezoelectric stack with a programmable DC power supply (Keithley model230) using either triangular, square, or sinusoidal waveforms with afrequency between 5 and 50 Hz. In practice, a triangular waveform wasused to produce a triangular voltage waveform of 0-100V at 10 Hz thatwas applied to the piezoelectric stack to produce a 10 Hz oscillation ofthe piezoelectric stack with a total displacement magnitude ofapproximately 6 μm. The piezoelectric stack used to apply oscillatingforce to each composite article was attached to a stage that allowed thecomposite article to be preloaded with a known force during measurement.The range of preloaded force could be varied from 0.1 N to 10 N. Thus,the oscillating force from the piezoelectric stack was superimposed upona known force preloaded during measurement. The force applied to thecomposite article during measurement was measured using a forcesensitive resistor (Flexiforce model A201) in contact with one of thestainless-steel electrodes of the fixture. The response of the forcesensitive resistor was calibrated in units of Newtons of force beforeuse by means of a top loading balance. During each measurement, thepreloaded force, the oscillating force peak-to-peak magnitude, and thepeak-to-peak magnitude of the oscillating coulombic charge generated bythe composite article during measurement was simultaneously recorded asa function of time. The peak-to-peak magnitude of the oscillating chargefrom the composite article was determined. The peak-to-peak magnitude ofthe oscillating force applied to the composite article was determined.The ratio of the magnitude of the oscillating charge to the magnitude ofthe oscillating force was calculated and taken as the experimentalpiezoelectric charge coefficient of the composite article. In allmeasurements reported herein, the oscillating force and preloaded forceon the piezoelectric layer under test was applied parallel to thedirection in which the piezoelectric layer under test was poled. This isthe measurement configuration that those skilled in the art recognize asthe measurement configuration for the piezoelectric charge coefficientdesignated as d₃₃ or d_(T). The piezoelectric charge coefficient d₃₃ hasunits of picocoulombs per Newton (pC/N) and is a measurement of how muchelectronic charge a piezoelectric layer or device containing apiezoelectric layer will generate under stress. For many applications,like energy harvesting and sensor design, larger values of d₃₃ aredesirable, regardless of the type of piezoelectric material employed.For the present invention, when relative composite article response isgiven, the piezoelectric response of the piezoelectric layer under testis taken as the ratio of the piezoelectric charge coefficient of thecomposite article under test to the piezoelectric coefficient determinedfor a chosen reference article under similar or identical condition.

TABLE VIII below shows the d₃₃ values measured at a given forceoscillation (the force oscillation being measured as a delta forcevalue) in comparison to a reference article. All reported measurementswere carried out at a preloaded force of less than 2 Newtons (N). Thoseskilled in the art of piezoelectric material characterization willrecognize that it is generally accepted that a preloaded force less than2 Newtons is recommended for reliable measurement of piezoelectriccoefficients with Berlincourt type measurement instruments.

The reference article used for evaluating the composite articles ofComparative Examples 5-9 and Invention Examples 22 to 43, 45-46 was acommercially available, silver-electroded, electrically poled,poly(vinylidene fluoride) membrane (part number 1-1004346-0 from TEConnectivity). The reference article used for evaluating the compositearticle of Invention Example 44 was a piece of nickel-electroded leadzirconate titanate (type 5H; Navy Type VI) piezoelectric ceramic. Thefollowing TABLE VIII provides the values for the magnitude of theoscillating force (Delta F in Newtons) during measurement, d₃₃ of eachcomposite article, d₃₃ of the reference article (“d₃₃-ref”), and theratio of the composite article d₃₃ value to the d₃₃-ref value. When thisratio was greater than 1.15, the piezoelectric response of the compositearticle was greater than the response of the reference article under themeasurement conditions. The d₃₃ values reported in TABLE VIIIdemonstrate large increases in the d₃₃ piezoelectric coefficient when anelectrically-conducting layer (ECL-P) prepared according to the presentinvention was arranged on the noted PL and preloaded force of 2N or lesswas present.

TABLE VIII Example Dry PL Material EC or EC-P Composition Delta F (N)d₃₃ d₃₃-ref Ratio Comparative 5 28 μm PVDF; Ag-electroded (1- Silvernanoparticles; Acrysol ™ 0.55 36.17 31.83 1.13 1004346-0 TEConnectivity) RM-12W; water Invention 22 28 μm PVDF; Ag-electroded (1-Silver nanoparticles; Acrysol ™ 0.75 100.11 20.00 5.01 1004346-0 TEConnectivity) RM-12W; d50 of 46 μm crosslinked polystyrene particles;water Invention 23 28 μm PVDF; Ag-electroded (1- Silver nanoparticles;Acrysol ™ 0.62 84.35 46.72 1.81 1004346-0 TE Connectivity) RM-12W; d50of 91 μm crosslinked polystyrene particles; water Invention 24 28 μmPVDF; Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.84 49.96 41.871.19 1004346-0 TE Connectivity) RM-12W; d50 of 201 μm crosslinkedpolystyrene particles; water Invention 25 28 μm PVDF; Ag-electroded (1-Silver nanoparticles; Acrysol ™ 0.76 83.25 44.26 1.88 1004346-0 TEConnectivity) RM-12W; d50 of 7 μm alumino silicate ceramic microspheres;water Invention 26 28 μm PVDF; Ag-electroded (1- Silver nanoparticles;Acrysol ™ 0.78 99.60 23.62 4.22 1004346-0 TE Connectivity) RM-12W; d50of 9.4 μm alumino silicate ceramic microspheres; water Invention 27 28μm PVDF; Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.74 94.4229.30 3.22 1004346-0 TE Connectivity) RM-12W; d50 of 10.7 μm aluminosilicate ceramic microspheres; water Invention 28 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.78 56.70 50.52 1.121004346-0 TE Connectivity) RM-12W; 1 weight % of d50 7.75 μm crosslinkedaliphatic polyurethane microspheres; water Invention 29 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.74 50.88 54.67 0.931004346-0 TE Connectivity) RM-12W; 2 weight % of d50 7.75 μm crosslinkedaliphatic polyurethane microspheres; water Invention 30 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.86 27.30 15.73 1.741004346-0 TE Connectivity) RM-12W; 7.5 weight % of d50 7.75 μmcrosslinked aliphatic poly- urethane microspheres; water Invention 31 28μm PVDF; Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.74 56.3455.25 1.02 1004346-0 TE Connectivity) RM-12W; 12.5 weight % of d50 7.75μm crosslinked aliphatic poly- urethane microspheres; water Invention 3228 μm PVDF; Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.53102.47 28.42 3.60 1004346-0 TE Connectivity) RM-12W; d50 of 10.7 μmcrosslinked aliphatic polyurethane microspheres; water Invention 33 28μm PVDF; Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.97 25.1421.43 1.17 1004346-0 TE Connectivity) RM-12W; d50 of 21 μm crosslinkedaliphatic polyurethane microspheres; water Invention 34 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.63 105.01 36.06 2.911004346-0 TE Connectivity) RM-12W; d50 of 16.5 μm low densityfilamentary nickel powder; water Invention 35 28 μm PVDF; Ag-electroded(1- Silver nanoparticles; Acrysol ™ 0.44 43.54 34.47 1.26 1004346-0 TEConnectivity) RM-12W; d50 of 34 μm irregular platelet nickel particles;water Invention 36 28 μm PVDF; Ag-electroded (1- Silver nanoparticles;Acrysol ™ 0.65 15.95 43.54 0.36 1004346-0 TE Connectivity) RM-12W; d50of 56 μm fine flake nickel platelets; water Invention 37 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; Acrysol ™ 0.63 40.71 35.63 1.141004346-0 TE Connectivity) RM-12W; d50 of 13 μm spiky nickel particles;water Invention 38 28 μm PVDF; Ag-electroded (1- Silver nanoparticles;poly(vinyl 0.73 22.39 17.49 1.28 1004346-0 TE Connectivity) pyrrolidone)K30; d50 of 9.4 μm alumino silicate ceramic microspheres; waterInvention 39 28 μm PVDF; Ag-electroded (1- Silver nanoparticles;poly(3,4- 0.80 92.36 53.71 1.72 1004346-0 TE Connectivity)ethylenedixoythiophene) polystyrene sulfonate; d50 of 9.4 μm aluminosilicate ceramic microspheres; water Invention 40 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; thermoplastic 0.82 92.20 51.931.78 1004346-0 TE Connectivity) poly(vinyl butyral) resin; d50 of 9.4 μmalumino silicate ceramic microspheres; water Invention 41 28 μm PVDF;Ag-electroded (1- Silver nanoparticles; ethoxylated 0.50 68.98 21.663.19 1004346-0 TE Connectivity) trimethylol-propane triacrylate;4,4′-azobis(4-cyanovaleric acid); d50 of 9.4 μm alumino silicate ceramicmicrospheres; water Invention 42 28 μm PVDF; Ag-electroded (1-Poly(3,4-ethylenedixoy-thiophene) 0.78 47.27 17.47 2.71 1004346-0 TEConnectivity) polystyrene sulfonate; ethylene glycol; d50 of 9.4 μmalumino silicate ceramic microspheres; water Comparative 6 28 μm PVDF;Ag-electroded (1- NovaCentrix HPS-021LV:HPS- 0.55 46.56 32.01 1.451004346-0 TE Connectivity) 030LV (75:25 weight ratio) Comparative 7 28μm PVDF; Ag-electroded (1- NovaCentrix HPS-021LV:HPS- 0.80 28.13 25.621.10 1004346-0 TE Connectivity) 030LV (50:50 weight ratio) Comparative 828 μm PVDF; Ag-electroded (1- NovaCentrix HPS-021LV:HPS- 0.63 32.8128.39 1.16 1004346-0 TE Connectivity) 030LV (25:75 weight ratio)Invention 43 110 um PVDF; Ag-electroded (3- Silver nanoparticles;Acrysol ™ 0.83 43.53 35.79 1.22 1004347-0 TE Connectivity) RM-12W; d50of 9.4 μm alumino silicate ceramic microspheres; water Invention 44 LeadZirconate Titanate (type 5H; Navy Silver nanoparticles; Acrysol ™ 0.67775.17 626.10 1.24 Type VI) RM-12W; d50 of 9.4 μm alumino silicateceramic microspheres; water Comparative 9 28 μm PVDF; no ECL Bare PVDFwith no ECL (for 0.65 18.68 20.52 0.91 (1-1003352-0 TE Connectivity)measurement purposes the steel anvils were used as electrodes)

FIGS. 26 and 27 are graphical representations of the d₃₃ piezoelectriccharge coefficients determined for use of a particular piezoelectriclayer with and without different types of EC or EC-P compositions as afunction of applied preload force. The trend lines illustrating thetrends in the different data sets that are plotted in the graphicalrepresentations shown in FIGS. 26 and 27 are intended only as a guidefor the reader. In both FIGS. 26 and 27, the reference article compriseda silver-electroded, electrically poled, poly(vinylidene fluoride)membrane (obtained from TE Connectivity, 1-1004346-0). The referencearticle data are represented by data points around the lower graphicaltrend lines in each of FIGS. 26 and 27.

FIG. 26 compares the d₃₃ response as a function of preloaded force ofthe reference article to the response of the composite article preparedfor Comparative Example 5 described above, comprising a PL that isidentical with that of the reference article and having a silvernanoparticle dry ECL (electrode) prepared using the Comparative Example1 EC composition described above [that is, no (b) particles are present]that is overlying and in contact both physically and electrically withone surface of the PL. FIG. 26 demonstrates that a dry ECL (electrode)with a uniform Young's modulus that is applied to the dry PL has a d₃₃response that is identical with that of the reference article. In otherwords, the composite article of Comparative Example 5 shows the samepiezoelectric response as the reference article within the limit of themeasurement method. The ratio of the d₃₃ values of the composite articleof Comparative Example 5 to that of the reference article was alwaysless than 1.15 in the preloaded region 0 and 5 N. That is, the d33 valueof the composite article of Comparative Example 5 is always within 15%of the d₃₃ value of the reference article in the force preloaded regionbetween 0 N and 5 N.

FIG. 27 compares the d₃₃ response as a function of preloaded force ofthe reference article to the response of the composite article preparedfor Invention Example 26 that comprised a dry PL identical to that ofthe reference article, but also comprised a dry ECL-P (electrode)prepared using the EC-P composition of Invention Example 5 overlying andin contact both physically and electrically with the surface of the dryPL. The Invention Example 5 EC-P composition comprised 7.5% by weight ofthe d50 of 9.4 μm alumino silicate ceramic microspheres as the (b)particles along with silver nanoparticles as the (a)electrically-conductive material. The additional composite article dryECL-P of Invention Example 26 exhibits a non-uniform and spatiallyvarying Young's modulus when it is measure at different physicallocations on the dry ECL-P. The non-uniform and spatially varyingYoung's modulus is attributed to the presence of the alumino-silicateceramic microsphere (b) particles whose Young's modulus is differentfrom that of the surrounding (a) electrically-conductive material. Thealumino-silicate ceramic microsphere (b) particles used in InventionExample 26 are electrical insulators.

The data shown in FIG. 27 demonstrate that a composite article accordingto the present invention having a dry ECL-P containing (b) particlesexhibits significantly larger d₃₃ response than the reference article inwhich the dry ECL contains no (b) particles, within the limit of themeasurement method. The ratio of the d33 values for Invention Example 26can be as large as 14 in the region of preloaded force between 0 and 3N. FIG. 27 also illustrates that the use of a composite articleaccording to the present invention provides enhanced response of a dryPL particularly at low applied forces in the region of applied forcethat is useful for haptic applications such as the design of tactileforce sensitive electrical interfaces that are responsive to humantouch. FIG. 27 further demonstrates that the use of composite articlesaccording to the present invention exhibit enhanced response of a dry PLat low applied forces so that it approaches that of piezoelectricceramic materials as shown by the comparison of the data from FIG. 27with the data for the composite article for Invention Example 44 shownabove in TABLE VIII and comparison of the data from FIG. 27 with thedata for the nickel electroded lead zirconate titanate (type 5H; NavyType VI) reference article with no dry ECL-P shown above in TABLE VIII.Dry PL's in composite articles like those of Invention Example 26 thatexhibit an enhanced d₃₃ response as shown in FIG. 27 are also useful ina variety of elements such as energy harvesters of vibrational energyand as elements within physical force sensors comprised of piezoelectrictransducers where a generation of a voltage signal in response tovibration or force is desired.

Effect from the Presence of (b) Particles:

The results from the composite articles prepared in Comparative Example5 and Invention Example 22 utilizing the ECL and ECL-P compositions ofComparative Example 1 and Invention Example 1, respectively, demonstratethat the presence of the (b) particles provides an enhanced effect onthe piezoelectric charge coefficient d₃₃. The resistivity of the dry ECLof Comparative Example 5 was 0.015 ohm-cm while that of the compositearticle of Invention Example 22 was 0.7 ohm-cm. Note that the higherresistivity material provided a high d₃₃ response (see TABLE VIII),demonstrating that the measured d₃₃ is not directly predictable fromelectrical properties of the dry ECL in the composite article.

Effect of (b) Particle Loading:

The results from the composite articles prepared for Invention Examples28-31 using the EC-P compositions of Invention Examples 7-10,respectively, where the aliphatic crosslinked polyurethane particleswere added as (b) particles at 1 weight %, 2 weight %, 7.5 weight %, and12.5 weight %, respectively, demonstrate the effect of (b) particleloading on the piezoelectric charge coefficient d₃₃. The d₃₃ effect wasgreater at (b) particle loadings of 1 weight % or more. The resistivityof the EC-P composition provided for Invention Example 9 was 0.07ohm-cm.

Effect of High Modulus (b) Particle Size:

The results from the composite articles prepared for Invention Examples22-24 using the EC-P compositions of Invention Example 1-3,respectively, containing crosslinked polystyrene micrometer-sized (b)particles of d50 of 46, 91, or 201 μm in size, respectively, demonstratethe effect of (b) particle size on d₃₃ (see TABLE VIII). The data showthat there is an increase in d₃₃ due to the presence of particles overthe entire tested range of (b) particle sizes.

The results from the composite articles prepared for Invention Examples34-37 using the EC-P compositions of Invention Examples 13-16,respectively, containing high modulus (b) particles that containedelectrically-conductive nickel, also demonstrate that the use ofelectrically-conductive (b) particles can provide an enhanced d₃₃piezoelectric charge coefficient in the composite article. It should benoted that comparison of Invention Examples 34-37 with InventionExamples 22-24 demonstrates that both magnetic and non-magneticparticles can be used in the EC-P to enhance d₃₃ of the dry PL.

Effect of Low Modulus (b) Particle Size:

The results from the composite articles prepared for Example 30, 32, and33 using the EC-P compositions of Invention 9, 11, and 12, respectively,containing low modulus (b) particles having a d50 of 7.75 μm, 10.7 μm,and 21 μm, respectively, demonstrate the d₃₃ increase that was observedacross the noted range of such (b) particle sizes of crosslinkedaliphatic polyurethane particles.

Effect of Differing (b) Particle Sizes of the Same Young's Modulus:

The results from the composite articles prepared for ComparativeExamples 6-8 using the ECL compositions of Comparative Examples 2-4,respectively, where the (b) particles are of the same Young's modulus asthe (a) electrically-conductive material, silver, but having 2 distinctor bimodal distributions, in the nanometer and micrometer range, showthe lack of enhanced d₃₃ over the (b) particle size range. TheseComparative Examples demonstrate the necessity for the (b) particles tohave a Young's modulus different from that of the (a)electrically-conductive material.

Effect of PL Composition:

The results from composite article prepared for Invention Example 26using the EC-P composition of Invention Example 5 and a PL comprisingpoly(vinylidene fluoride) and from the composite article prepared forInvention Example 44 using the EC-P composition of Invention Example 5and a lead zirconium titanate ceramic sheet as the PL demonstrate thatan enhanced d₃₃ piezoelectric charge coefficient can be achievedaccording to the present invention for a variety of PL materials. Thus,the present invention and its advantages can be achieved using a varietyof dry PL materials regardless of the Young's modulus of the PL layer.

Effect of (c) Binder Material:

The results from composite articles prepared for Invention Examples 26and 38-41 using the EC-P compositions of Invention Examples 5 and 17-20,respectively, demonstrate the usefulness of a variety of rheologymodifiers as (c) binder materials for making inventive EC-P compositionsfor preparing inventive composite articles. The resistivity of the EC-Pcomposition used for making the composite article in Example 41 of 116ohm-cm is a useful value.

Effect of Various (a) Electrically-Conductive Materials:

The results from composite articles prepared according to InventionExamples 26 and 42 using the EC-P compositions of Invention Examples 5and Example 21, respectively, demonstrate the ability of using various(a) electrically-conductive materials into which the (b) particles aredispersed. To characterize the range of electrical properties that areuseful for the composite articles according to the present invention,the electrical resistivity of composite articles prepared from the EC-Pcompositions of Invention Examples 5 and 21 were measured. Theresistivity of the composite article prepared for Invention Example 42was 80 ohm-cm and resistivity of the composite article prepared forInvention Example 26 was 0.015 ohm-cm. It is desirable for theelectrical resistivity of a composite article according to the presentinvention to be less than 10,000 ohm-cm, less than 500 ohm-cm, or moreparticularly, less than 150 ohm-cm.

Invention Examples 45-46

These examples demonstrate that the (a) electrically conducting materialemployed in the composite articles according to the present invention isnot limited to the silver nanoparticle-containing formulations describedabove for Invention Examples 1-20. Silver inks purchased fromNovaCentrix were used as the (a) electrically-conductive component in adry ECL-P while additional (b) particles, Polybead-50 (50 μm), wereadded to form the EC-P composition. Invention Example 45 included theuse of HPS-021LV silver ink (NovaCentrix d50=0.29 μm silver particleswith a bimodal distribution including micrometer-sized particles) as the(a) electrically-conductive material, and Invention Example 46 includedthe use of HPS-030LV silver ink (NovaCentrix d50=0.16 μm silverparticles) as the (a) electrically-conductive material. The (b)particles were added to a weighed amount of the (a)electrically-conductive material in a container and mixed with aFlackTek Speedmixer™ DAC 150 speedmixer to provide each EC-Pcomposition.

Inventive Examples 45 and 46 were prepared by similar methods disclosedabove. The dry PL, a Ag-electroded PVDF membrane (1-1004346-0 TEConnectivity), was secured onto a coating block while each EC-Pcomposition was applied using a pipette and the droplet(s) were spreadevenly on the dry PL planar surface using a Meyer rod to provide a wetcoverage of 22 μm.

TABLES IX, X, XI, and XII below provide additional information andresults for these Invention Examples.

TABLE IX (d) (b) (a) Silver (c) Binder Solvent Particles (b) to (a)Invention Particles Solid Material Solid (b) Particles Medium d50 WeightExample weight % weight % Solid Weight % Weight % (μm) Ratio Type of (b)Particles 45 71.25 5.05 5 18.7 46 0.07 5 weight % of sphericalcrosslinked poly(styrene-co-divinyl benzene-co- ethylvinyl benzene(Polybead-50) 46 71.25 5.05 5 18.7 46 0.07 5 weight % of sphericalcrosslinked poly(styrene-co-divinyl benzene-co- ethylvinyl benzene(Polybead-50)

TABLE X Invention Solid weight % of (a) Solid weight % Solid Weight % of(b) Particles Example Silver particles of (c) Polymer (b) Particles d50(μm) Type of (b) Particles 45 87.6 6.2 6.2 46 5 weight % of sphericalcrosslinked poly(styrene- co-divinyl benzene-co-ethylvinyl benzene(Polybead-50) 46 87.6 6.2 6.2 46 5 weight % of spherical crosslinkedpoly(styrene- co-divinyl benzene-co-ethylvinyl benzene (Polybead-50)

TABLE XI TABLE IX ECL or ECL-P Wet Example EC or EC-P CompositionComposition Dry PL Material Thickness (μm) 47 5 weight % of sphericalcrosslinked poly(styrene-co- 45 28 μm PVDF; Ag-electroded 22 divinylbenzene-co-ethylvinyl benzene (Polybead ® (1-1004346-0 TE Connectivity)50) 48 5 weight % of spherical crosslinked poly(styrene-co- 46 28 μmPVDF; Ag-electroded 22 divinyl benzene-co-ethylvinyl benzene (Polybead ®(1-1004346-0 TE Connectivity) 50)

TABLE XII Example PL Material EC or EC-P Composition Delta F (N) d33d33-ref Ratio 47 28 μm PVDF; Ag-electroded 5 weight % of sphericalcrosslinked 0.51 58.6 22.6 2.59 (1-1004346-0 TE Connectivity)poly(styrene-co-divinyl benzene-co-ethylvinyl benzene (Polybead ® 50) 4828 μm PVDF; Ag-electroded 5 weight % of spherical crosslinked 0.49 49.926.3 1.90 (1-1004346-0 TE Connectivity) poly(styrene-co-divinylbenzene-co-ethylvinyl benzene (Polybead ® 50)

The d₃₃ piezoelectric charge coefficient ratio shown in TABLE XI abovedemonstrates that composite articles can be prepared according to thepresent invention using an EC-P composition that was formulated usingcommercially available materials. Thus, the inventive EC-P compositionshave wide compositional breadth.

Invention Example 47

The EC composition of Comparative Example 1 above was used but with theaddition of 5 weight % solids of alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410,effective d50 particle size of 9.4 μm %) and 0.25 weight % of Dynol™ 810fluorosurfactant in a FlackTek Speedmixer™ DAC 150 speedmixer for 1-3minutes at a speed >1500 rpm to create an inventive EC-P composition.

A composite article according to the present invention was prepared inthe following manner. A non-electroded (1-1003352-0 TE Connectivity) drypiezoelectric layer material (dry PL) in the form of a sheet or web wassecured on a coating block and the EC-P composition was applied to theopen PL surface by a pipette drop. The EC-P composition described abovewas spread evenly onto the dry PL by rod-coating techniques using Meyerrods to provide a wet lay-down of at least 22 μm and up to 86 μm.

Invention Example 48

An EC-P composition was prepared and a composite article was preparedusing a non-electroded (1-1003352-0 TE Connectivity) piezoelectricmaterial (dry PL) in the form of a sheet or web as described inInvention Example 47 to form a first dry ECL-P on one side of the dryPL, followed by drying. A second dry ECL-P was formed by applying thesame EC-P composition onto the opposite second supporting surface of thePL by a pipette drop, followed by drying. The second EC-P compositionwas spread evenly by rod-coating techniques using Meyer rods to providea wet lay-down of at least 22 μm and up to 86 followed by drying.

Further details about the EC-P compositions used in Invention Examples47 and 48 are provided in the following TABLES XIII and XIV.

TABLE XIII ECL Wet Thickness Example EC-P Composition Dry PL (μm)Invention 47 Silver nanoparticles; Acrysol ™ RM-12W; d50 of 28 μm PVDF(no commercial 22 9.4 μm alumino silicate ceramic microspheres;electrodes); (1-1003352-0 TE Dynol ™ 810; water Connectivity) Invention48 Silver nanoparticles; Acrysol ™ RM-12W; d50 of 28 μm PVDF (nocommercial 22 9.4 μm alumino silicate ceramic microspheres; electrodes);(1-1003352-0 TE Dynol ™ 810; water Connectivity)

TABLE XIV Invention Weight % (a) Silver Weight % (c) Binder Weight % (b)(b) Particles D50 Example Nanoparticles Material Particle (μm) (b)Particles Type 47 94.4 0.125 5 9.4 solid alkali alumino silicate ceramicmicrosphere particles (3M Ceramic Microspheres White Grade W-410) 4894.4 0.125 5 9.4 solid alkali alumino silicate ceramic microsphereparticles (3M Ceramic Microspheres White Grade W-410)

The evaluation of the piezoelectric charge coefficient d₃₃ for thecomposite article of Invention Example 47, the electrode on one side ofthe dry PL was the prepared dry ECL-P, and the electrode on the oppositeside of the dry PL was a 12.5 mm diameter cylindrical steel electrode.The following TABLE XV provides the evaluation data for both InventionExamples 47 and 48, similarly to that shown in TABLE XII above.

TABLE XV Invention @ Delta F Example Dry PL ECL-P Description (N) d₃₃d₃₃-ref Ratio 47 28 μm PVDF (no commercial Silver nanoparticles;Acrysol ™ RM-12W; water; 0.78 21.66 14.4 1.5 electrodes); (TE1-1003352-0); 1 Dynol ™ 810; solid alkali alumino silicate ceramicfabricated electrode with (b) microsphere particles (3M CeramicMicrospheres particles White Grade W-410) with an effective d50 of 9.4μm 48 28 μm PVDF (no commercial Silver nanoparticles; Acrysol ™ RM-12W;water; 0.66 63.6 18.2 3.5 electrodes); (TE 1-1003352-0); 2 Dynol ™ 810;solid alkali alumino silicate ceramic fabricated electrodes with (b)microsphere particles (3M Ceramic Microspheres particles White GradeW-410) with an effective d50 of 9.4 μm

FIG. 28 illustrates the significant enhancement of d₃₃ as theoscillating force was reduced to less than 1 N for both the compositearticle of Invention Example 47 having a dry ECL-P on one side of thedry PL only, and for the composite article of Invention Example 48 thatcomprise a dry ECL-P on both sides of the dry PL. The trend linesillustrating the trends in the data sets that are plotted in thegraphical representation of FIG. 28 are intended only as a guide for theobserver.

FIG. 29 depicts the significant enhancement of d₃₃ as the preloadedforce was reduced to less than 5 N, for both the composite article ofInvention Example 47 having a dry ECL-P on one side of the dry PL only,and for the composite article of Invention Example 48 that comprise adry ECL-P on both sides of the dry PL. The trend lines illustrating thetrends in the data sets that are plotted in the graphical representationof FIG. 29 are intended only as a guide for the observer.

The following examples demonstrate the preparation and evaluation ofcomposite articles according to the present invention which contain atleast one dry DL-P in place of a dry ECL-P.

Invention Examples 49-50

As described above, composite articles according to the presentinvention can also be designed with a dielectric material that includes(b) particles with a d50 larger than 1 μm wherein the (b) particles areorganic or inorganic. The dielectric material can be arranged as a dryDL-P that is spatially located at any suitable location in a compositearticle also comprising one or more dry ECL's and a dry PL according tothe present invention. Alternatively, the dielectric material containing(b) particles can be discontinuous but in the same plane. That is, therecan be gaps in the dielectric material in the plane, for example,containing non-electrically-connected co-planar patterned electrodes,with or without the same or different (b) particles. In addition, thedielectric material containing (b) particles can also function as anoutermost dry protective layer that can be discontinuous or continuous.

FIG. 43 shows composite article 400 comprised of first dry ECL 415 thatis contiguous with a planar surface (not shown) of dry PL 30; second dryECL 420 that is contiguous with an opposing planar surface (not shown)of dry PL 30; and dry DL-P 355 that is contiguous with Ag electrode(second dry ECL) 420.

In Invention Example 49 (illustrated in FIG. 43), (b) particles (notshown) were incorporated into dielectric material composition to form aD-P composition that was applied contiguously to form dry PL 30 toprovide dry DL-P 355 in the following manner.

Polybead-50 was added to provide (b) particles at 5 weight % to asolution of Butvar™ 76, 14 weight %, dissolved in ethyl alcohol. Theresulting D-P composition was coated as described in other InventiveExamples contiguous to the Ag-electroded commercial PVDF dry PL 30 at awet thickness of 22 μm. Small diameter platinum lead wire 405 was placedbetween Ag electrode (second dry ECL) 420 and dry DL-P 355 to provideelectrical communication from Ag electrode (second dry ECL) 420 toexternal measurement system 410 for making measurements. Small platinumlead wire 405 allowed the collection of the generated charge from thesurface of dry PL 30. Electrical continuity between small platinum leadwire 405 and Ag electrode 420 was verified by a resistance meter.

In Invention Example 50 illustrated in FIG. 44, composite article 425has the same layer arrangement as composite article 400 illustrated inFIG. 43, but external measurement system 410 was differently arranged asdescribed below.

TABLE XVI below provides the weight % composition of dry DL-P 355. TABLEXVII below provides the dry weight % composition of dry DL-P 355 afterformation on first dry ECL 415. TABLE XVIII below defines the compositearticle layer stack as dry DL-P/dry ECL/dry PL/dry ECL (referencenumbers 355/420/30/415).

TABLE XVI Solid weight Weight % Solid weight % % of Solid Weight of (d)(b) Particles (b) to (a) Invention of (a) Silver dielectric % of (b)Solvent d50 Weight Example particles material Particles Medium (μm)Ratio Type of (b) Particles 49 0 14.2 0.75 85 46 0.07 5 weight % ofspherical crosslinked poly(styrene- co-divinyl benzene-co- ethylvinylbenzene (Polybead-50)

TABLE XVII Solid weight % (b) Particles Invention Solid weight % of ofdielectric Solid Weight % of d50 Example (a) Silver particles material(b) Particles (μm) Type of (b) Particles 49 0 95 5 46 5 weight % ofspherical crosslinked poly(styrene-co-divinyl benzene-co- ethylvinylbenzene (Polybead ® 50)

TABLE XVIII TABLE XVI Dry ECL/dry PL/dry ECL DL-P Wet Invention ExampleD-P Composition Composition Material Thickness (μm) 50 5 weight % ofspherical crosslinked 49 28 μm PVDF; Ag-electroded 22poly(styrene-co-divinyl benzene-co- (1-1004346-0 TE ethylvinyl benzene(Polybead ® 50) in Connectivity) Butvar ™ 76

The piezoelectric charge constant d₃₃ of composite article 400 inInvention Example 49 (FIG. 43) was measured using the Berlincourt methodby making electrical contact with small platinum lead wire 405 that wascontiguous with second dry ECL 420 and dry DL-P 355, and a secondelectrical contact was made on first dry ECL 415 that was contiguouswith the opposing surface (not shown) of dry PL 30 using one of twostainless steel anvils 430 in a Berlincourt apparatus. These connectionsallowed direct collection of the charge generated in dry PL 30 byelectrical contact with first dry ECL 415 and second dry ECL 420 thatwas in electrical communication with small platinum lead wire 405 wherecharge was collected at the surface of the Ag-electroded (second dry ECL420) PVDF PF 30.

In Invention Example 50 (FIG. 44), the piezoelectric charge constant d₃₃of composite article 425 was measured using the Berlincourt method bymaking electrical contact with dry DL-P 355 using both stainless steelanvils 430. Electrical contact was made on the opposing surface (notshown) of dry PL 30 by a second of stainless steel anvils 430 in themeasurement apparatus. There was no electrical contact to small platinumlead wire 405.

Data obtained from these measurements are recorded below in TABLE XIX.

TABLE XIX Invention Dry ECL/dry PL/dry ECL Measurement Example MaterialD-P Composition configuration Delta F (N) d33 d33-ref Ratio 49 28 μmPVDF; Ag-electroded 5 weight % of spherical crosslinked FIG. 43 0.2875.3 29.0 2.6 (1-1004346-0 TE poly(styrene-co-divinyl benzene-co-Connectivity) ethylvinyl benzene (Polybead ® 50) in Butvar ™ 76 50 28 μmPVDF; Ag-electroded 5 weight % of spherical crosslinked FIG. 44 0.2246.6 34.1 1.37 (1-1004346-0 TE poly(styrene-co-divinyl benzene-co-Connectivity) ethylvinyl benzene (Polybead ® 50) in Butvar ™ 76

Composite article 400 of Invention Example 49 (FIG. 43) having dry DL-P355 showed enhanced d₃₃ response. Dry DL-P 355 was spatially positionedlike an outermost dry protective overcoat. However, in otherembodiments, a dry DL-P can be spatially located at any location whereinit is contiguous with at least one layer within the composite article.The discussion provided above along with various illustrations in thevarious figures provide guidance as to other suitable arrangements of adry DL-P according to the present invention.

Surprisingly, the composite article of Invention Example 50 where thed₃₃ response was measured through dry DL-P 355 as illustrated in theconfiguration shown in FIG. 44, exhibited an enhanced d₃₃ response.Without wishing to be bound by theory, the unexpected enhancement in thed₃₃ response of composite article 425 of Invention Example 50 suggeststhat useful image charges can be generated in the dry DL-P.

The enhanced d₃₃ responses of a composite article according to thepresent invention, measured in the two different measurementconfigurations shown in FIGS. 43 and 44 demonstrate that the position ofa dry DL-P is not limited.

Another method can be used to provide non-uniformity in mechanicalstrain at a PL and its surface including patterning or printing onto thesurface of the PL discrete features of a material having a Young'smodulus different from that of the PL itself. This method can be carriedout using patterns of either conductive materials or non-conductivematerials to form a desirable composite article. In the embodimentswhere conductive materials are patterned, the conductive materials canbe the necessary electrical contact to have electrical communicationwith the PL if they are patterned in a way that is consistent withelectrical continuity as understood by someone skilled in the art ofelectrode design. In the embodiments where non-conductive materials ordielectric materials are used, it would then be necessary to alsoinclude an ECL or ECL-P in the article or device to provide electricalcommunication with the PL for utility. When no (b) particles arepresent, such as in an ECL, the ECL Young's modulus is different fromthat of the patterned material by ±10% (as defined above). In addition,the Young's modulus of the PL is different from that of the patternedmaterial by ±10% (as defined above). However, the ECL and PL can havethe same or different Young's moduli.

Two exemplary embodiments of such a composite article are shown in FIGS.47A and 47B wherein different exemplary dielectric patterns arecontiguous with a PL and an ECL. In FIG. 47A, composite article 520 isshown with one side or surface of PL 460 disposed contiguously withpatterned dielectric layer 515 that is illustrated as a checkerboardpattern comprised of squares with dimensions on the order of 20×20 μmwith a height of 1 μm, but the same or different patterns can havedifferent area and height dimensions. Patterned dielectric layer 515 isalso contiguous with second ECL 80. Additionally, exposed areas (areashaving no patterned material) of PL 460 can be optionally contiguouswith second ECL 80. The opposing side or surface of PL 460 is contiguousand in contact with ECL 20.

In FIG. 47B, composite article 530 is shown with one side of surface ofPL 460 disposed contiguously with patterned dielectric layer 516 that isillustrated as a pattern of ellipses with dimensions on the order of14×54 μm with a height of 1 μm. The pitch of the ellipses within a rowis 96 μm and the pitch between the two rows of ellipses is 60 μm. Theellipses in each row are offset by 38 μm to form a two-dimensional cubicclose packed pattern. This pattern is, of course, illustrative only, andother similar patterns of different dimensions and arrangements can bedisposed on a PL. Patterned dielectric layer 516 is contiguous withsecond ECL 80. Additionally, exposed areas (areas having no patternedmaterial) of PL 460 can be optionally contiguous with second ECL 80. Theopposing side or surface of PL 460 is contiguous and in contact with ECL20.

Without wishing to be bound to a particular theory, it is believed thata patterned dielectric layer as illustrated in FIGS. 47A and 47B canfunction similarly to the b) particles as described above for theseveral inventive composite articles. When the Young's modulus of apatterned dielectric layer that is disposed contiguously with a PL isdifferent from the Young's modulus of the PL itself, then non-uniformstress can be generated in the PL upon application of an external force.Additionally, the Young's modulus of the patterned dielectric layer mustbe different from that of each ECL in order to generate non-uniformstress at the PL. The Young's modulus of the patterned dielectric layershould be different independently from that of the PL and each ECL by atleast 10%.

While such embodiments are not explicitly illustrated herein, it is alsopossible to use one or more ECL-P's in such composite articlescontaining a patterned dielectric layer in place of one or more ECL's.

Examples 51 and 52

Composite articles using the patterned dielectric layers shown in FIGS.47A and 47B were prepared in the following manner:

A relief image was created in a commercially available Flexcel NXprinting plate using standard conditions and processing chemistry, forexample as described in U.S. Pat. No. 8,034,540B2 (Zwadlo) and U.S. Pat.No. 9,250,527 (Kidnie), the disclosures of both of which is incorporatedherein by reference, for use to print a desired pattern of dielectricmaterial. The checkerboard pattern illustrated in FIG. 47A and theellipse pattern illustrated in FIG. 47B were printed using suitablerelief images in such flexographic printing plates. A commerciallyavailable flexographic printer (IGT Printability Tester from IGT TestingSystems) was used to print each patterned layer of photopolymerizablemonomer composition onto a commercially available poled PVDF substrateas the PL (1-1003352-0 TE Connectivity) using methods familiar to thoseskilled in the art of flexographic printing. The photopolymerizablemonomer composition contained, by weight, 58.5% of pentaerythritoltetraacrylate, 29.2% of hexanediol diacrylate, 5.3% of IRGACURE® 907,5.3% of IRGACURE® 184, and 1.8% of DAROCUR® TPO (Ciba,2,4,6-trimethylbenzoyl-diphenyl-phosphineoxide) as described forexample, in U.S. Patent Application Publications 2015/0322280 A1 (Jin etal.) and 2014/0327452 A1 (Petcavich et al.), the disclosures of both ofwhich are incorporated herein by reference.

Each printed pattern of photopolymerizable monomer composition wasphotocured using a commercially available UV curing station (Fusion UVCuring, Systems Corp. Model MC6R) to form a patterned dielectric layercomprised of a clear UV-crosslinked acrylate polymer.

The composite article of Example 51 comprised a poled PVDF substrate anda flexographically printed checkerboard patterned dielectric layer ofphotopolymerized acrylate polymer disposed thereon. The compositearticle of Example 52 comprised a poled PVDF substrate with a patterneddielectric layer of photopolymerized acrylate polymer comprised ofarranged rows of ellipses disposed thereon. In both Examples 51 and 52the feature size of the patterned dielectric layer was 10-200 μm havinga height of approximately 1 μm. The Young's modulus of the bare PVDF andthe Young's modulus of the dry photopolymerized acrylate polymercomposition was measured using nanoindentation methods to determine thehardness. Thus, the hardness of the flexographically printedphotopolymerized acrylate polymer was 0.929±0.143 GPa and the hardnessof the bare pre-poled PL comprised essentially of PVDF was 0.550±0.071GPa.

The piezoelectric coefficients for the composite articles of Examples 51and 52 were determined using the previously described Berlincourtmeasurement system and the same methods employed for evaluatingInventive Example 50. The d₃₃ piezoelectric charge coefficientsdetermined by the Berlincourt measurement method were 108 pC/N at adelta force of 0.75 N for Example 51 having the checker board patterneddielectric layer 515, and 196 pC/N at a delta force of 0.51 N forExample 52 for the ellipses-containing patterned dielectric layer 516.The calculated ratio of the measured d₃₃ value over the reference d33value was 2.55 and 4.2, respectively, for Examples 51 and 52.

The patterns that can be provided in such composite articles caninclude, but are not limited to, circles, squares, checker board,ellipses, stars, concentric circles, lines, crossed lines as in a gridpattern, crossed lines as in a hashed pattern, and any shapes orcombination of shapes and lines that can be desired and applied by thoseskilled in the art of applying patterns to surfaces. Patterns can beapplied using various printing articles and methods for their use,including, but are not limited to, flexographic printing plates andflexographic methods; lithographic printing plates and lithographicmethods, and other deposition apparatus, articles, and methods thatwould be readily apparent to one skilled in the art (including articlesand methods utilizing photolithographic masks). Correspondingly, thepatterned features of, for example, UV-cured photopolymerized polymercompositions can include, but are not limited to, flexographic printing,gravure printing, ink jet printing, screen printing, and lithographicpatterning or printing techniques. Those skilled in the art of applyingpatterns imagewise to surfaces will recognize that suitable patterns ofmaterials meeting the modulus requirements for the dielectric layerdescribed above can be formed by many different methods. Anon-exhaustive exemplary list of such means includes the use ofpatterned thermally curable materials, compression molding of patternedlayers, stamping of patterned layers and similar applique methods,photolithographic processes, and stenciling of patterned layers. Thus,although Examples 51 and 52 demonstrate the use flexographic printingplates to provide patterned dielectric layers comprised ofphotopolymerized polymers for generating non-uniform stress in a PL, thenovel concept of providing non-uniform stresses in the PL is not limitedto the use of dielectrics and other materials can be used to form thepatterned layer providing that the material has suitable mechanicalproperties when compared with the PL and any electrically conductivelayers that are present whether ECL or ECL-P.

FIG. 48A is a cross-sectional view of a simple reference unimorph (ormonomorph) cantilever beam 540 that is comprised of substrate 140, ECL20, PL 460, insulator (or insulating layer) 505 and second ECL 80.Second ECL 80 is disposed over and in contact with one side of PL 460and insulator 505. ECL 20 is in contact and contiguous with bothsubstrate 140 and PL 460 as well as insulator 505. Insulator 505 and PL460 are contiguous. The function of insulator 505 is to ensure thatthere is no electrical contact between ECL 20 and second ECL 80, and itcan be composed of any material having suitable electrically insulatingproperties having a resistance greater than 1E7 ohms (10 Megaohms).Suitable insulating layers include inorganic insulators such as siliconoxide (made using CVD or PECVD with TEOS), silicon oxide based glasses,and organic insulators like Kapton polymers or Teflon based polymers.Other suitable materials include glass-ceramic composites, fiberglasscomposites, non-conductive epoxies, and insulating imagable materialssuch as epoxies photoresists like SU-8, polyimide photoresists and othermaterials that would be readily apparent to one skilled in the art fromthis teaching.

FIG. 48B is a cross-sectional view of a novel unimorph (or monomorph)cantilever beam 550 that is comprised of substrate 140, ECL 20, PL 460,patterned dielectric layer of ellipses 516 (see FIG. 47B) insulator 505,and second ECL 80. Second ECL 80 is disposed over and in contact withone side of patterned dielectric layer 516 and insulator 505. Patterneddielectric layer 516 is disposed over, contiguous to, and in contactwith PL 460. ECL 20 is in contact with and contiguous to both substrate140 and PL 460 as well as insulator 505. Insulator 505, patterneddielectric layer 516, and PL 460 are contiguous and proximate to oneanother. The function of insulator 505 is to ensure that there is noelectrical contact between ECL 20 and second ECL 80.

FIG. 48C is a cross-sectional view of inventive unimorph (or monomorph)cantilever beam 560 that is comprised of substrate 140, ECL 20, PL 460,checkerboard patterned dielectric layer 515 (see FIG. 47A), insulator505, and second ECL 80. Second ECL 80 is disposed over and in contactwith one side of PL 460 and insulator 505. Patterned dielectric layer515 is disposed under, contiguous to, and in contact with PL 460. ECL 20is in contact and contiguous with both substrate 140 and patterneddielectric layer 515 as well as insulator 505. Insulator 505, dielectriclayer 515, and PL 460 are contiguous and proximate to one another. Thefunction of insulator 505 is to ensure that there is no electricalcontact between ECL 20 and second ECL 80.

Reference unimorph cantilever beam 540 and the unimorph cantilever beams550 and 560 of Examples 53 and 54, respectively, all as inertialdevices, were constructed using silver filled epoxy to form both ECL 20and second ECL 80 and a commercially available glass cover slide(Corning Cover Glass, GlassWorks, 24 mm×60 mm) as shown in FIGS. 48A-C.PL 460 was comprised of poled PVDF. The combination of the PL 460 witheither patterned dielectric layer 515 or 516 each of which is continuouswith and in proximate to PL 460 was prepared according to Examples 51and 52.

Reference unimorph cantilever beam 540 was prepared according to thelayer cross-section shown in FIG. 48A. Support 140 was composed of aglass material over which ECL 20 was disposed and comprised of a thincoating of electrically conductive silver-based epoxy (MG Chemicals,Silver Conductive Epoxy 8331), with a hardness of 0.248±0.170 Gpa, thathad been applied by blade coating; over which PL 460 was placed. Theelectrically-conductive silver-based epoxy was cured with the PL 460 inplace. A layer of insulating Kapton film was applied in the area ofexposed electrically-conductive silver-based epoxy to form insulator505. Second ECL 80 comprised of a second layer of silver-based epoxy wasthen applied to PL 460 and insulator 505, and cured. Electrical contactsare made by securing electrical leads to each layer of electricallyconductive silver-based epoxy.

Unimorph cantilever beam 550 of Example 53 was prepared according to theillustration of FIG. 48B in the same manner as reference unimorphcantilever beam 540 except that a combination of PL 460 with patterneddielectric layer 516 from Example 51 was used in place of PL 460 alone.Patterned dielectric layer 516 was positioned on PL 460 so that it wascontiguous with PL 460, which is contiguous with ECL 20, that in thisexample, was an electrically-conductive silver-based epoxy, which inturn, is contiguous with substrate 140. In other words, patterneddielectric layer 516 was disposed to be facing towards second ECL 80 andto also face outwards and away from support 140. As noted above, printeddielectric layer 516 was a pattern of ellipses of dimensions on theorder of 14×54 μm with a height of 1 μm.

Unimorph cantilever beam 560 of Example 54 was prepared according to thelayer cross-section shown in FIG. 48C in the same manner as referenceunimorph cantilever beam 540 except that a combination of PL 460 withdielectric layer 515 from Example 52 was used in place of PL 460 alone.Patterned dielectric layer 515 was positioned on PL 460 so that it wascontiguous with PL 460, which is contiguous with second ECL 80 that inthis example, was an electrically-conductive silver-based epoxy. Inother words, patterned dielectric layer 515 was disposed to be facingtowards ECL 20 and to also face inwards and towards support 140. Asnoted above, patterned dielectric layer 515 was a checker board patterncomprised of squares with dimensions on the order of 20×20 μm with aheight of 1 μm.

The capacitance and resistance for unimorph cantilever beams 550 and 560for Examples 53 and 54, respectively, and reference unimorph cantileverbeam 540 was measured at 1 kHz with a Fluke PM6303A LCR meter and aSencore LC102 Capacitor Inductor Analyzer as a low frequency measurementas described in more detail below, with the values provided below inTABLE XX.

Unimorph cantilever beam 540 and unimorph cantilever beams 550 and 560described above in Example 53 and 54, respectively, were each broughtinto mechanical communication with a support like support 230 shown inFIG. 31B to form inertial piezoelectric devices and each unimorphcantilever beam structure was vibrated while measuring the electricaloutput of the respectively PL. The measurement system for characterizingthe electrical characteristics of each unimorph cantilever beam wascomprised of electrically insulating mounting block that is mechanicallyequivalent to support 230 of FIG. 31B, which was used to hold the beamthat was mechanically fastened to a speaker cone driven by a voice coil(Parts Express model LW150-4). The electrical leads from each unimorphcantilever beam being tested were connected to binding post terminals toallow the charge generated by the respective PL to be measured byvarious instruments during vibrational excitation. The voice coilattached to the speaker cone was driven by an audio amplifier (CarverProfessional model PT-2400) that was used to amplify the waveform from awaveform generator (Agilent model 33220A). The gain of the audioamplifier was held constant during all measurements and the amplitudeand frequency of vibrational stimulus applied to each unimorphcantilever beam was controlled through the waveform applied to theamplifier. All waveforms used were symmetric sinusoidal waveforms with a50% duty cycle. The measurement system was equipped with a camera andappropriate optics to allow observation of the oscillating motion of thebeam as the voice coil was driven with sinusoidal waveforms.

The resonance frequency of each unimorph cantilever beam was determinedby two different measurements: 1) measurement of the maximum opencircuit voltage as a function of voice coil drive frequency at constantamplitude of the driving waveform; and 2) the optical observation ofmaximum displacement amplitude of each unimorph cantilever beam as afunction of voice coil drive frequency at constant amplitude of thedriving waveform. The open circuit voltage generated by the vibratingbeam was measured as a true RMS voltage using a digital volt meter withan impedance of 1 Megaohm (HP 3458A multimeter). The open circuitvoltage at resonant frequency of reference unimorph cantilever beam 540,unimorph cantilever beam 550 of Example 51, and unimorph cantilever beam560 of Example 52 at 100 mV drive amplitude were 0.871 V_(rms), 1.34V_(rms), and 0.857 V_(rms), respectively. The peak to peak outputvoltage of each unimorph cantilever beam under vibrational excitationwas either calculated from the measured V_(rms) or measured directlyusing a high impedance 1:1 amplifier (CoreTech Differential IsolationAmplifier model ISO-20-1V/V) and a digital storage oscilloscope(Tektronix TDS 2024B). The electrical power that can be extracted fromthe each unimorph cantilever beam during excitation was measured byconnecting the output of each to a known resistive load and measuringthe voltage drop across the load using a digital storage oscilloscopeand a high impedance 1:1 amplifier. The mean power dissipated into theresistive load of the circuit is calculated by taking the mean value ofthe waveform of the instantaneous power derived from the voltagewaveform using the relationship P=V²/R where V is the measured meanvoltage across the resistive load. The unimorph cantilever beam responseat the beam resonant frequency was characterized by measuring electricalpower at a constant resistive load as a function of voice coil driveamplitude and additionally by measuring the electrical power at constantdrive amplitude as a function of resistive load magnitude, as shown inFIGS. 49 and 50, respectively, wherein data for reference unimorphcantilever beam 540 are shown with dark triangles; data for unimorphcantilever beam 550 are shown with squares; and data for unimorphcantilever beam 560 are shown with circles.

The performance of each unimorph cantilever beam for vibrational energyharvesting with capacitive energy storage was assessed by measuring acapacitor charging curve using a VS148 full wave rectifying diode bridgecircuit and a known capacitance of 47 μfarads according to the methodsdescribed by Mao et al (Adv. Energy Mater. 2014, 1301624). The capacitorcharging curve was obtained using the following method: the ACelectrical output of each vibrating unimorph cantilever beam atmechanical resonance was applied to the input of the full wave rectifierbridge and the rectified DC electrical output was applied to a knowncapacitor that stored the generated electrical energy. The voltageacross the capacitor as a function of time was measured with a highimpedance preamplifier and a data acquisition system to acquire thecapacitor charging curve as a function of time, and is shown in FIG. 51for each of reference unimorph cantilever beam 540 (data shown with darkline), 550 for Example 53 (data shown with wide dark line), and 560 forExample 54 (data shown with light grey line). The maximum instantaneouspower stored in the capacitor is related to the maximum slope of thecapacitor voltage as a function of time curve and was determined bycalculating the maximum value of the derivative of the capacitorcharging curve. An improved cantilever beam vibrational energy harvesterwould show at least one of the following characteristics relative toreference uniform cantilever beam 540: 1) a larger voltage measuredacross the capacitor when the capacitor circuit has reached a steadystate indicating that more energy has been stored in the capacitor; or2) a decrease in the amount of time required to charge the capacitor toa given voltage indicating that the amount of energy per unit timestored in the capacitor has increased.

The previously described maximum instantaneous power in units ofmicrowatts was taken as a relative measure of the amount of energy perunit time that was generated by unimorph cantilever beams 550 and 560 ofExamples 53 and 54, respectively. TABLE XX below shows that unimorphcantilever beams 550 and 560 that performed as energy harvester inertialdevices, exhibited improved performance relative to reference unimorphcantilever beam 540 as shown either by the superior open circuit voltageor superior instantaneous power generation.

Without wishing to be bound by theory, it is thought that the improvedperformance of the unimorph cantilever beams 550 and 560 used as energyharvesting inertial devices is attributed to the non-uniform straingenerated by patterned dielectric layers 515 and 516, respectively,applied to PL 460 upon application of force, where the Young's modulusof the material comprising the each patterned dielectric layer wasdifferent from that of the PL by at least 10% (meaning 10% or more) andalso different from that of the Young's modulus of each ECL by at least10%. Those skilled in the art of cantilever beam vibrational energyharvesters will recognize that the results presented here demonstratethat the composite articles described in FIGS. 47A and 47B show noveland unexpected improvements in d₃₁ in addition to the improvement of d₃₃as measured using the Berlincourt method. Thus, the use of patternedlayers with different Young's modulus provides a method of improvingboth d₃₃ and d₃₁ piezoelectric charge coefficients of piezoelectriclayers.

Those skilled in the art of vibrational energy harvesters will recognizethat such useful patterned dielectric layers applied to piezoelectriclayers can be easily generated on cantilever beam MEMS structures usingknown photolithographic methods employing suitable photosensitiveresists such as, for example, SU-8 epoxy based resists, polyimide-basedresists, and acrylate-based resists. The examples of energy harvesters,both inertial and kinetic that have been disclosed herein are intendedto be non-restrictive. Further contemplated applications of patternedlayers on a PL are contemplated to fall within the inventive scope ofthis disclosure.

The capacitance and resistance for unimorph cantilever beams 550 and 560for Examples 53 and 54, respectively, and reference unimorph cantileverbeam 540 were measured at 1 kHz with a Fluke PM6303A Automatic RCL meterand a Sencore LC102 Capacitor Inductor Analyzer as a low frequencymeasurement. As those skilled in the art of electrical measurementsunderstand, the RCL meter automatically determines the dominantelectrical behavior exhibited by the device under test and calculatesthe electrical parameters for the appropriate series or parallelarrangement of capacitive and resistive elements. All the unimorphcantilever beams exhibited the same RCL behavior when tested at 1 kHzwith the Automatic RCL meter and the RCL values for each unimorphcantilever beam device under test were determined using an equivalentcircuit model comprised of a capacitor and resistor in parallel. Thevalues of the parallel capacitance and parallel resistance for eachsample tested at 1 kHz are denoted in TABLE XX by the parameters Cp inunits of picofarads (pF) and Rp in units of ohms (ohms), respectively.In TABLE XX below, the low frequency capacitance is given in units ofpicofarads (pF).

TABLE XX Fluke PM6303A LCR Sencore Meter (Calculated Instant- OpenAnalyzer Electrical Parameters aneous Circuit Capacitance at 1 kHz)Power Voltage pF Cp (pF) Rp (ohms) (μW) (V_(rms)) Example 53 1051 10016.37 × 10⁶ 0.62 1.34 Example 54 751 716 8.10 × 10⁶ 0.31 0.857 Reference1157 1104 6.40 × 10⁶ 0.27 0.871

The indentation modulus and indentation hardness of a patterneddielectric layer comprised of photopolymerized acrylate polymer, thePVDF piezoelectric polymer layer, and the silver filled epoxy layer usedin Examples 53 and 54 were measured by nanoindentation methods. Thenanoindentation behavior of each sample was studied using an MTSNanoindenter XP produced by MTS Systems Cooperation, (Oak Ridge, Tenn.).Each sample was conditioned for 24 hours at 23° C./50% RH prior totesting. After this conditioning period, ten replicate load-displacementcurves were generated for each sample using a Berkovich indenterobtained from MTS. A maximum load of 0.1 mN and a loading/unloading rateof 0.007 mN/second were used in all cases. A 30-second hold time wasincorporated into the loading profile prior to unloading in order toallow time for the sample being tested to approach equilibrium. Aftereach indentation experiment was completed, the Oliver and Pharr analysismethod was used to determine an average indentation modulus and hardnessvalue for each sample.

The silver-based epoxy and photopolymerized acrylate polymer (SPOC1)samples were coated on glass, and thus no additional sample preparationsteps were necessary. The free-standing film of bare PVDF sample wasglued to a quartz slide using a cyanoacrylate adhesive prior tomeasurement. Those skilled in the art of micromechanicalcharacterization of materials recognize that the indentation modulusmeasured here is the elastic modulus or Young's modulus of a film asmeasured using nanoindentation techniques as described above.

TABLE XXI below presents a summary of the indentation modulus and theindentation hardness values obtained for the three noted samples. Thedata in TABLE XXI demonstrate that the average value of the Young'smodulus of the polymer used to prepare the patterned dielectric layer inExamples 53 and 54 measured by a nanoindentation method is at least 10%different from the average value of the Young's modulus of the silverfilled epoxy material used as the ECL in Examples 53 and 54 when allmaterials are measured by the same method. Additionally, the data inTABLE XXI demonstrate that the average value of the Young's modulus ofthe polymer used to prepare the patterned dielectric layer in Examples53 and 54 measured by a nanoindentation method is at least 10% differentfrom the average value of the Young's modulus of the PVDF PL used inExamples 53 and 54 when all materials are measured by the samenanoindentation method.

TABLE XXI Indentation Modulus Indentation Hardness Material Layer (GPa)(GPa) Silver-based Epoxy 9.07 +/− 4.53 0.248 +/− 0.170 PhotopolymerizedAcrylate 14.87 +/− 1.38  0.929 +/− 0.143 Polymer (SPOC1) Bare PVDF Film8.27 +/− 0.60 0.550 +/− 0.071

Composite articles according to such description illustrated in Examples53 and 54 can be defined at least as comprising:

1) a first dry piezoelectric layer (first dry PL) comprising apiezoelectric material and having first and second opposing surfaces,and

2) one or more dry additional layers arranged contiguously with at leastone of the first and second opposing surfaces of the first dry PL,wherein at least one dry additional layer is a patterned dry additionallayer that has a Young's modulus that is different from the Young'smodulus of the first dry piezoelectric layer by at least 10%.

In some embodiments, one or more dry additional layers areelectrically-conductive dry additional layers (such as ECL's asdescribed above), and the Young's modulus of the patterned dryadditional layer can also be different from the Young's modulus of eachelectrically-conductive dry additional layer. First and second ECUs canbe present in some embodiments, one or both being contiguous with thepatterned dry additional layer.

Moreover, any of the one or more electrically-conductive dry additionallayers can be an ECL-P as described above, comprising (b) particles asdescribed above.

One or more of the dry additional layers can be electrically insulating,and comprise a dielectric material such as in an DL or DL-P as describedabove.

Such composite articles can further comprise a support as such materialsas described above.

Each patterned dry additional layer can be disposed on at least onesurface of the PL using suitable patterning means including but notlimited to flexographic printing using suitable flexographic printingplates having relief images; or by using lithographic printing plates inlithographic printing methods. Any type of pattern can be provided asalong as it provides non-uniform stress to the PL when physical force isapplied.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

-   10 composite article-   15 composite article-   20 dry electrically-conductive layer (dry ECL)-   25 dry electrically-conductive layer dry (ECL-P)-   30 dry piezoelectric layer (dry PL)-   35 (b) particles-   40 composite article-   45 composite article-   50 second dry electrically-conductive layer (second dry ECL-P)-   55 (b) particles-   60 composite article-   65 composite article-   70 composite article-   75 composite article-   80 second dry electrically-conductive layer (second dry ECL)-   85 composite article-   90 composite article-   95 composite article-   100 composite article-   105 composite article-   110 composite article-   115 composite article-   120 composite article-   125 composite article-   130 outermost dry protective layer-   135 composite article-   140 substrate-   145 composite article-   150 dry dielectric layer (dry DL-P)-   155 second dry dielectric layer (second dry DL-P)-   159 electromechanical model-   160 spring-   165 dashpot-   170 piezoelectric material-   175 support-   180 electrodes-   185 mass-   190 external electrical circuit load-   195 kinetic (or kinematic) piezoelectric device-   200 direct applied force-   205 inertial piezoelectric device-   210 secondary inertial applied force-   215 mechanical assembly-   220 inertial piezoelectric device-   225 tip mass-   230 support means-   235 inertial piezoelectric device-   240 clamping mechanism support-   245 piezoelectric capacitor-   250 electrical communication means-   255 diode bridge-   260 diode-   265 diode-   270 diode-   275 diode-   280 energy storage device-   285 energy storing rectifying circuit-   290 electrical switches-   300 force-sensitive touch display-   305 capacitive touch sensor-   310 force sensing backplane-   315 signal processing electronics-   320 resistive touch sensor-   325 force-sensitive touch display-   330 composite article-   335 non-electrically-connected co-planar patterned electrodes-   340 non-electrically-connected co-planar patterned electrodes-   345 substrate-   350 piezoelectric layer (dry PL)-   355 dry dielectric layer (dry DL-P)-   360 opposing surface-   365 composite article-   370 planar surface-   375 dielectric material-   378 opposing surface-   380 composite article-   385 opposing planar surface-   390 non-electrically-connected co-planar electrode with (b)    particles-   395 non-electrically-connected co-planar electrode with (b)    particles-   400 composite article-   405 small platinum lead wire-   410 external measurement system-   415 first dry electrically-conductive layer (first dry ECL)-   420 second dry electrically-conductive layer (second dry ECL)-   425 composite article-   430 stainless steel anvils-   440 composite article-   445 non-electrically-connected co-planar patterned electrode-   450 non-electrically-connected co-planar patterned electrode-   455 opposing surface-   460 dry piezoelectric layer (dry PL)-   465 composite article-   470 non-electrically-connected co-planar patterned electrode-   475 non-electrically-connected co-planar patterned electrode-   480 opposing surface-   485 dry piezoelectric layer (dry PL)-   505 insulator (or insulating layer)-   515 patterned dielectric layer (having checker board pattern)-   516 patterned dielectric layer (having pattern of ellipses)-   520 composite article-   530 composite article-   540 reference unimorph cantilever beam-   550 unimorph cantilever beam-   560 unimorph cantilever beam

The invention claimed is:
 1. A composite article comprising: 1) a firstdry piezoelectric layer (first dry PL) comprising a piezoelectricmaterial and having first and second opposing surfaces, and 2) a pair ofnon-electrically-connected co-planar patterned electrodes that arearranged contiguously with at least one of the first and second opposingsurfaces of the first dry PL, each of the pair ofnon-electrically-connected co-planar patterned electrodes consistingessentially of: (a) an electrically-conductive material; and (b)particles distributed within the (a) electrically-conductive material,the (b) particles having a Young's modulus that is different from theYoung's modulus of the (a) electrically-conductive material by at least10%, and which (b) particles have a d50 of at least 500 nm and up to andincluding 500 μm and a polydispersity coefficient of less than or equalto 3, provided that the weight ratio of the (b) particles to the (a)electrically-conductive material is at least 0.01:1 and up to andincluding 10:1, and provided that: when each of the pair ofnon-electrically-connected co-planar patterned electrodes is arrangedadjacent to an insulating substrate, it exhibits a resistivity of lessthan 10,000 ohms-cm, and optionally, each of the pair ofnon-electrically-connected co-planar patterned electrodes furtherincludes (c) a binder material that is non-electrically-conductive andhas a weight average molecular weight of at least 5,000.
 2. Thecomposite article of claim 1, wherein the (a) electrically-conductivematerial comprises particles having a median equivalent spherical volumediameter of at least 1 nm and up to and including 1000 μm and apolydispersity coefficient that is less than or equal to
 2. 3. Thecomposite article of claim 1, wherein the (a) electrically-conductivematerial comprises one or more of silver, gold, platinum, palladium,copper, nickel, titanium, and an electrically-conductive form of carbon.4. The composite article of claim 1, wherein the (a)electrically-conductive material is an electrically-conductive organicpolymer.
 5. The composite article of claim 1, wherein the (a)electrically-conductive material consists essentially of silvernanoparticles having a d50 of less than or equal to 60 gm and a d90 ofless than or equal to 500 μm and a polydispersity that is less than orequal to
 1. 6. The composite article of claim 1, wherein when each ofthe pair of non-electrically-connected co-planar patterned electrodes isarranged contiguously with an insulating substrate, it exhibits aresistivity of less than 500 ohm-cm.
 7. The composite article of claim1, wherein the (a) electrically-conductive material is present in anamount of at least 2 weight % and up to and including 99 weight %, basedon the total weight of each of the pair of non-electrically-connectedco-planar patterned electrodes.
 8. The composite article of claim 1,wherein the (b) particles are composed of one or more polymericmaterials.
 9. The composite article of claim 1, wherein the (b)particles are composed of one or more inorganic materials.
 10. Thecomposite article of claim 1, wherein the (c) binder material is presentand comprises one or more polyurethanes, acrylate polymers, polyvinylacetals, or polyacrylate precursors to an acrylate polymer.
 11. Thecomposite article of claim 1, wherein the (c) binder material is presentin an amount of at least 0.1 weight % and up to and including 10 weight%, based on the total weight of the at least one dry ECL-P.
 12. Thecomposite article of claim 1, further comprising an insulating substrateand the pair of non-electrically-connected co-planar patternedelectrodes are arranged contiguously between the insulating substrateand the first dry PL.
 13. The composite article of claim 12, furthercomprising a first dry electrically-conductive layer containing no (b)particles (first dry ECL), which first dry ECL is arranged contiguouslywith the second opposing surface of the first dry PL.
 14. The compositearticle of claim 13, further comprising a first dryelectrically-conductive layer containing (b) particles (first dry ECL-P)that is arranged contiguously with the first dry ECL that is arrangedcontiguously with the second opposing surface of the first dry PL. 15.The composite article of claim 1, further comprising dielectric materialarranged in the same plane as and between the pair ofnon-electrically-connected co-planar patterned electrodes.
 16. Thecomposite article of claim 1, wherein the (b) particles have apolydispersity coefficient that is less than or equal to 1.5.
 17. Thecomposite article of claim 1, wherein the (b) particles have apolydispersity coefficient that is less than or equal to 1.25.
 18. Thecomposite article of claim 1, wherein the first dry PL comprises betaphase polyvinylidene fluoride.
 19. The composite article of claim 1,further comprising a second dry piezoelectric layer (second dry PL)comprising a piezoelectric material, which is arranged contiguously withan electrically-conductive layer or a pair of non-electrically-connectedco-planar patterned electrodes that are arranged between the first dryPL and the second dry PL.